How should I prepare for my 2 level 6 players going into an extremely dangerous area?

[MonkeySage]

I'm struggling with a conundrum: My players, each level 6, are about to go to a region with these qualities:
20% normal magic, 50% wild magic, 30% dead magic
No Gravity or objective directional gravity, depending on where you are.
Floating rocks, some the size beach balls, some the size of houses...
Wildly fluctuating temperatures...

This region was the battle ground for a massive exchange between two magocratic empires, and has never recovered.

What monsters could they find here? How do I provide a reasonable, but not overbearing challenge for my players, while also giving the area justice for how dangerous it is supposed to be (it is the single thing that a gold dragon in my setting is afraid of).

[Mike Miller]

Sounds like an astral dreadnaught should be flying around there. Any [Air] creature could work with the gravity issues. Did you think about what creatures existed in that region before the war-splosion?
Maybe undead resulted from the magical cataclysm? Boatloads of undead to choose from...

[Telok]

Well, as you get closer to the area you get to use more and weirder monsters. Within the area you probably want to use living spells. They're a template applied to a spell that turns them into an ooze creature with an engulf effect that applies the spell to it's victims.

[Ashiel]

I'm struggling with a conundrum: My players, each level 6, are about to go to a region with these qualities:
20% normal magic, 50% wild magic, 30% dead magic
No Gravity or objective directional gravity, depending on where you are.
Floating rocks, some the size beach balls, some the size of houses...
Wildly fluctuating temperatures...

This region was the battle ground for a massive exchange between two magocratic empires, and has never recovered.

What monsters could they find here? How do I provide a reasonable, but not overbearing challenge for my players, while also giving the area justice for how dangerous it is supposed to be (it is the single thing that a gold dragon in my setting is afraid of).

Play around with the bizarre terrain using stuff from the environmental rules. Play with the directional gravity by having areas where parties end up exploring ruins castlevania newgame+ style where they're running through places upside down and dealing with the curious footing of the ceilings being the floors. Have various locations that rapidly change across the environment spectrum, or are bizarre combinations (such as a hurricane and volcano in an area that's freezing cold), or having things like rivers and lakes that are just suspended in the air, where you walk or swim through them.

As for creatures, just refluff a bunch of animals and stuff from the bestiary. If you happen to use Spheres of Might/Power, toss some Magic Training or Transformation feats onto some of them to give them bizarre supernatural powers. Alternatively, you can just make some small ad-hoc adjustments, apply templates, or even change no stats at all but just describe creatures in peculiar ways, shapes, colors, etc.

For example, you could use stats like the Giant Eagles and simply describe them as some bizarre flying creatures that happen to live on the floating biomes and soar between them hunting. Doesn't actually have to be an eagle. If you wanted to tweak them slightly you could do things like lowering their flight speed and dividing it off into other types of speeds (so like fly 50 ft., move 20 ft., climb 20 ft.) and let them nest by clinging onto the floating cliffsides.

You could also advance a few creatures in size or apply some templates and alter their environments. For example, if you took an Assassin Vine, doubled its HD and increased its size a few times, and have it just appear to be a giant root system hanging down from one of the clumps of floating rocks, or weeds growing out of a pool of water. You could drop the Half-Dragon template onto it and suddenly you have this plant-beast that sprouts claws and soars through the air and has blossoms that belch acid, fire, or lightning.

[Calthropstu]

Some things I use to chase players out of areas that are completely "nope, you're gonna die."

"You see a huge demon fighting a gargantuan golem. You watch it try to use magic to escape but the magic fails. The golem begins smashing it to a bloody pulp until it no longer moves or regenerates. The golem looks in your general direction..."

"Two dragons are battling. One red, the other blue. Lightning scorches an area close to you. The dragons do not seem to notice you, but getting caught in that mess will mean almost certain death."

"You see a troop of iron clad skeletons, about 50 strong. They are obviously more recent as they have the armor of your country's knights. Their gear has ceased to be magical, or even functional. Rust is seen on several pieces of armor that is usually enchanted to prevent such."

"The ground seems to undulate in a cavern nearby. You take out a spyglass to look more closely. You eventually figure out that the valley is crawling with thousands of rust monsters.

Etc.

[Ashiel]

Some things I use to chase players out of areas that are completely "nope, you're gonna die."

"You see a huge demon fighting a gargantuan golem. You watch it try to use magic to escape but the magic fails. The golem begins smashing it to a bloody pulp until it no longer moves or regenerates. The golem looks in your general direction..."

"Two dragons are battling. One red, the other blue. Lightning scorches an area close to you. The dragons do not seem to notice you, but getting caught in that mess will mean almost certain death."

"You see a troop of iron clad skeletons, about 50 strong. They are obviously more recent as they have the armor of your country's knights. Their gear has ceased to be magical, or even functional. Rust is seen on several pieces of armor that is usually enchanted to prevent such."

"The ground seems to undulate in a cavern nearby. You take out a spyglass to look more closely. You eventually figure out that the valley is crawling with thousands of rust monsters.

Etc.

Why even have the areas then? It seems like an absolutely wonderful opportunity to have a great adventure in an exotic and strange area. The dead magic thing seems super lame since randomly party members just have all their abilities turn off, but a spellwarped wonderland in and of itself sounds pretty neat if it was approached from an adventure standpoint and not a "how do I poop on my player's parade" standpoint.

[Asmotherion]

Any aberation. Perhaps some undead casters remaining still fighting the war with their mindless minions. Tortured souls with ghost template, wraiths, shadows etc. Dead bodies and dismembered corpses flying around. Devils and Demons fighting over claim of the dead souls.

[Zanos]

Why even have the areas then? It seems like an absolutely wonderful opportunity to have a great adventure in an exotic and strange area. The dead magic thing seems super lame since randomly party members just have all their abilities turn off, but a spellwarped wonderland in and of itself sounds pretty neat if it was approached from an adventure standpoint and a "how do I poop on my player's parade" standpoint.

Not every area in the setting is appropriate for every level of play. If the players walked through a portal to the Demomweb Pits on purpose at level 2 with no method of escape I'd probably just tell them to hand in their sheets after warning them not do it 50 times. I'd definitely classify an area permanently warped by a massive magical war a 'high level zone', although personally I'd avoid an area with randomly function magic even at level 20 unless I had a specific reason to go there.

They can always come back later when they've got more under their belt.

[Calthropstu]

Why even have the areas then? It seems like an absolutely wonderful opportunity to have a great adventure in an exotic and strange area. The dead magic thing seems super lame since randomly party members just have all their abilities turn off, but a spellwarped wonderland in and of itself sounds pretty neat if it was approached from an adventure standpoint and a "how do I poop on my player's parade" standpoint.

Yes. Absolutely. But 3.5 assumes "appropriate challenges." This would be my way of telling the players "There are no appropriate challenges here. Come back later." To be fair, this in and of itself can be fun, trying to sprint through desperately trying to avoid monsters that will squish you flat. My world is fairly fleshed out and has numerous dungeons that are already set up. Getting through high level areas as low level PCs would be exceedingly difficult. It's like trying to say "Ok guys, we've hit level 2. Let's go into Gnoll territory" and being surprised when you run into gnolls who mop the floor with the party.

[Ashiel]

Yes. Absolutely. But 3.5 assumes "appropriate challenges." This would be my way of telling the players "There are no appropriate challenges here. Come back later." To be fair, this in and of itself can be fun, trying to sprint through desperately trying to avoid monsters that will squish you flat. My world is fairly fleshed out and has numerous dungeons that are already set up. Getting through high level areas as low level PCs would be exceedingly difficult. It's like trying to say "Ok guys, we've hit level 2. Let's go into Gnoll territory" and being surprised when you run into gnolls who mop the floor with the party.

But every area in a typical D&D campaign is filled with high and low level challenges. If anything at all in the books is to be believed (monster ecologies, encounter tables, etc), whether you're walking around in a field of grass, some hills, a forest, hot or cold, above ground or under, on the water or in it, you can be beset by encounters well into the upper teens and beyond. Like if you're wandering around some temperate hills, you might encounter a gang of hill giants (2-5), a band (6-8), a raiding party (9-12 + 1d4 dire wolves), or heaven forbid a tribe (13–30 + 35% noncombatants plus 1 barbarian or fighter chief of 4th–6th level, 11–16 dire wolves, 1–4 ogres, and 13–20 orc slaves). Even just the lowly gang is anywhere from a CR 9 to CR 12 encounter.

That's not counting any of the myriad other creatures that happen to wander and roam temperate hills like hobgoblins or wyverns (wyverns frequently travel in groups of 3-6, and in 3.5 they grew up to 21HD and gargantuan size).

I guess it seems silly to me, because literally everywhere is dangerous and full of high level stuff. The idea just seems to be that you should avoid the high level stuff when you are yourself not high level (if you're roaming an area and notice dire wolf footprints, don't go that way; if you see a hill giant fort, don't go that way; if you're wandering along and your band of merry misfits is suddenly beset by wyverns, abandon your mule and seek the cover of trees; etc).

Going into a spellwarped land seems like it would just be its own brand of food chain, and it seems like a wasted opportunity to not play around with it if that's something the PCs are into. I'd dare say that as long as you have random pockets of dead magic or magic that doesn't work correctly, then low levels is about the only time playing in such an environment would actually be fun because those levels are the least reliant on magic to function.

[Ashiel]

I'm struggling with a conundrum: My players, each level 6, are about to go to a region with these qualities:
20% normal magic, 50% wild magic, 30% dead magic
No Gravity or objective directional gravity, depending on where you are.
Floating rocks, some the size beach balls, some the size of houses...
Wildly fluctuating temperatures...

This region was the battle ground for a massive exchange between two magocratic empires, and has never recovered.

What monsters could they find here? How do I provide a reasonable, but not overbearing challenge for my players, while also giving the area justice for how dangerous it is supposed to be (it is the single thing that a gold dragon in my setting is afraid of).

Also, I wanted to point out that "the only thing a gold dragon is afraid of" can mean a lot of things. Depending the dragon's age, size, views, and more, it could be that he's afraid of it because it's something he or she doesn't actually understand (living for seemingly forever and yet is completely flabbergasted by this anomaly), or fears that the corruption may spread, or it's a terrible reminder that no matter how powerful he or she is that some humans could just come and ruin reality itself, or it is unsettled because its breath weapons and magical powers just don't work at all in large portions of the region which is super spooky. This would especially be true in the case of megafauna like fiendish tyrannosaur that are more than capable of injuring an adult gold dragon without their magical powers (said tyrannosaurus would have DR 10 that the wyrm couldn't overcome, could swallow him whole, etc; and at 5 CRs below the wyrm to boot).

It definitely doesn't require there to be a bunch of super godlike beings or a maralith behind every rock to strike fear into the hearts of an a CR 15+ dragon. Humans are afraid of most bugs that are inconsequential to them. Just watch grown men scatter like geese when a wasp pops out from beneath the woodpile. In that strange land where magic sometimes doesn't work, there are environments and creatures that can hurt the wyrm and make his innate magics go away. That alone should seem very frightening.

Further Ideas
Still fiddling with the idea of the subjective and directional gravities, but lava flows could be neat things to include. While total immersion is a death sentence for most characters without heavy fire resistance (between 30-50d6 points of damage depending on the lingering damage roll), simply coming into contact with lava is only 2-5d6 points of damage. This makes small lava flows really practical for interesting environments even for lower level characters. Having areas where little balls of lava "bloom" out of the ground like flowers or fountains makes for some interesting "don't stand there" possibilities.

Similar situation with things like boiling water.

The trap rules can be used to create "natural" hazards like spells that won't end, areas where mini-planar wars are happening (resetting summon monster effects that just pour fresh summons into an area every round on the round), and so on. These can also be sapient magic traps to represent areas that are possessed by malevolent spirits that control the power of the spells. Or you could even make it a heroic thing where players have to reach and destroy a giant statue or something (the trap) to release the entrapped spirit (whose soul is being used to power nearby magics, etc) and allow them to pass on rather than being trapped in this bizarre land for untold times.

You might even have areas that are like a magical ultimate ninja course.

Some examples might be things like...
An area with several flaming sphere traps that each produce up to two flaming spheres and chase the party members around with them every round while the party is trying to navigate through a rocky and uneven area enclosed by ice with lava veins running through the walls like blood pumping through them (maybe you're actually inside some sort of inert magical creature and the flaming spheres are part of its immune system).

Strange plants or gardens that turn hostile when disturbed as the areas are suddenly covered in spike growths and squirt acid arrows. Bonus points if you include some garden keepers like resolute (simple template) giant wasp fluffed as bees or similar who are naturally at home in such an environment but are non-hostile as long as you're not destroying the garden.

Maybe find a village of awakened animals and plants who now revere and worship a resetting magic awaken trap as the sight-gifter. Perhaps your players find these creatures who suddenly all speak the common tongue trying their best to form into a society and want some advice, or help. Maybe they wish to hear stories of the outside world, or maybe even ask for the party's help with a problem they are having. Perhaps after the party successfully helps the sapient animals and plants they are celebrated and brought before the sacred awakener object where they are granted a boon similar to the one succubi grant except its a +2 sacred bonus to an ability score for their good deed done for the budding community of sapient animals. This could be a great opportunity to inject some roleplaying and some cute light hearted fun into an otherwise strange an alien land as you find a little tribe of animals trying to figure out how to do things like build houses, use tools, and not eat each other. In fact, maybe the problem they want help with is you going to get the awakener's sister-god the provisioner (a resetting create food and water and purify food and drink trap) to help the animals live together without the need for eating each other.

[RNightstalker]

Can the players handle the gravity problem? Are they primarily spellcasters? Will they be lambs to slaughter in the DMZ? What I'm really asking is, can your players handle the environment to begin with, let alone adding monsters to it?

[Calthropstu]

But every area in a typical D&D campaign is filled with high and low level challenges. If anything at all in the books is to be believed (monster ecologies, encounter tables, etc), whether you're walking around in a field of grass, some hills, a forest, hot or cold, above ground or under, on the water or in it, you can be beset by encounters well into the upper teens and beyond. Like if you're wandering around some temperate hills, you might encounter a gang of hill giants (2-5), a band (6-8), a raiding party (9-12 + 1d4 dire wolves), or heaven forbid a tribe (13–30 + 35% noncombatants plus 1 barbarian or fighter chief of 4th–6th level, 11–16 dire wolves, 1–4 ogres, and 13–20 orc slaves). Even just the lowly gang is anywhere from a CR 9 to CR 12 encounter.

That's not counting any of the myriad other creatures that happen to wander and roam temperate hills like hobgoblins or wyverns (wyverns frequently travel in groups of 3-6, and in 3.5 they grew up to 21HD and gargantuan size).

I guess it seems silly to me, because literally everywhere is dangerous and full of high level stuff. The idea just seems to be that you should avoid the high level stuff when you are yourself not high level (if you're roaming an area and notice dire wolf footprints, don't go that way; if you see a hill giant fort, don't go that way; if you're wandering along and your band of merry misfits is suddenly beset by wyverns, abandon your mule and seek the cover of trees; etc).

Going into a spellwarped land seems like it would just be its own brand of food chain, and it seems like a wasted opportunity to not play around with it if that's something the PCs are into. I'd dare say that as long as you have random pockets of dead magic or magic that doesn't work correctly, then low levels is about the only time playing in such an environment would actually be fun because those levels are the least reliant on magic to function.

If I am building a dead magic zone, wild magic zone or other "lets mess with magic" type area, there's going to be a good reason for it. And that reason isn't going to be "whee let's play around with dead magic." Even if it was naturally or accidentally created, high level monsters and npcs would visit or even reside in it. Where better to place dangerous artifacts, seriously problematic prisoners, magical seals for maintaining a bbeg's prison... The reason such a place would have large concentrations of high powered monsters would be the exact same reasons the PCs would want to go there themselves. And the area would be designed around guarding what was in the zone appropriately. At least, that's how I would handle it.

[Ashiel]

If I am building a dead magic zone, wild magic zone or other "lets mess with magic" type area, there's going to be a good reason for it. And that reason isn't going to be "whee let's play around with dead magic." Even if it was naturally or accidentally created, high level monsters and npcs would visit or even reside in it. Where better to place dangerous artifacts, seriously problematic prisoners, magical seals for maintaining a bbeg's prison... The reason such a place would have large concentrations of high powered monsters would be the exact same reasons the PCs would want to go there themselves. And the area would be designed around guarding what was in the zone appropriately. At least, that's how I would handle it.

I was under the impression that the OP already had a good reason for it (an unintended disaster). A reason that largely seemed completely unrelated to the intentions or machinations of others, and would only fit into those of the opportunistic and flexible, unless the region was especially old already and not something relatively recent.

Perhaps I have the wrong idea but, it seemed to me that the OP wasn't necessarily looking to crush his PCs or keep them out of the land they wished to explore, but to get ideas of how to make it exciting and figure out what sorts of wild and wondrous things could reside within. Why do we not offer up help and ideas rather than insist on bending what was asked for?

How should I prepare for my 2 level 6 players going into an extremely dangerous area?
I'm struggling with a conundrum: My players, each level 6, are about to go to a region with these qualities:
20% normal magic, 50% wild magic, 30% dead magic
No Gravity or objective directional gravity, depending on where you are.
Floating rocks, some the size beach balls, some the size of houses...
Wildly fluctuating temperatures...

This region was the battle ground for a massive exchange between two magocratic empires, and has never recovered.

What monsters could they find here? How do I provide a reasonable, but not overbearing challenge for my players, while also giving the area justice for how dangerous it is supposed to be (it is the single thing that a gold dragon in my setting is afraid of).

Gravity: Since we're not dealing with an actual plane but small regions on a planet, it would probably be a good idea to figure out the limits of objectionable gravity. It seems very unlikely that there's just an infinite "pillar" extending out into the cosmos in every location that gravity points in a direction other than "down". Because of this, consider looking at the reverse gravity spell for a good idea how to handle these locations. This could easily create situations where people "fall" into the air and get stuck there, and in many cases could explain why there are floating boulders (they hit the end of the area and just sit there).

This can allow you to have some really neat situations where players do things like tossing grappling hooks outside of the area and climb "down" or across the bizarre gravity fields to more stable gravity. It also allows you to more easily adjudicate where the odd gravity begins, ends, and how it affects the world and the things around it. Since things float when they hit the "bottom" of the area, you can have entire upside down or sideways pathways and trails that the PCs can move about and on. This could even be a really cool opportunity to engage in some neat 3d encounters without being in the water or flying.

EDITS: Fixed typo.

[Calthropstu]

I was under the impression that the OP already had a good reason for it (an unintended disaster). A reason that largely seemed completely unrelated to the intentions or machinations of others, and would only fit into those of the opportunistic and flexible, unless the region was especially old already and not something relatively recent.

Perhaps I have the wrong idea but, it seemed to me that the OP wasn't necessarily looking to crush his PCs or keep them out of the land they wished to explore, but to get ideas of how to make it exciting and figure out what sorts of wild and wondrous things could reside within. Why do we not offer up help and ideas rather than insist on bending what was asked for?

I think I did just that. "Run away from the currently engaged monstrosities" is not an overbearing challenge. It sets the right tone the op wants to portray. Likewise, a bunch of dead knights serving as a warning is, in no way, an overbearing challenge. In fact, it is a lack of a challenge that sets a grim tone for the area.

Another good idea would be to run into cultists (or whatever group their current chief opponent belongs to) who are injured, bedraggled and severely hampered by damaged armor after a battle with bebiliths. Being forced off course by obviously overpowered enemies (involving numerous survival checks) would be a great way to set the tone as well. Smaller monsters survive only by avoiding the larger monstrosities, and you could have the PCs fight such, but if they chase the enemies when they flee, they run the risk of entering seriously dangerous territory.

There would be near constant terror by the PCs.

[Zanos]

But every area in a typical D&D campaign is filled with high and low level challenges. If anything at all in the books is to be believed (monster ecologies, encounter tables, etc), whether you're walking around in a field of grass, some hills, a forest, hot or cold, above ground or under, on the water or in it, you can be beset by encounters well into the upper teens and beyond. Like if you're wandering around some temperate hills, you might encounter a gang of hill giants (2-5), a band (6-8), a raiding party (9-12 + 1d4 dire wolves), or heaven forbid a tribe (13–30 + 35% noncombatants plus 1 barbarian or fighter chief of 4th–6th level, 11–16 dire wolves, 1–4 ogres, and 13–20 orc slaves). Even just the lowly gang is anywhere from a CR 9 to CR 12 encounter.

Those are generic areas, not specific ones. If my setting contains a set of temperate hills that are largely controlled by hill giants, I'm not going to remove the hill giants from that area just because some goofballs decided to go there at level 1 despite my warnings. There are really places you shouldn't got at lower levels. Probably not smart to go through a portal to the lower planes or journey to a dragon graveyard, for example.

[Calthropstu]

Those are generic areas, not specific ones. If my setting contains a set of temperate hills that are largely controlled by hill giants, I'm not going to remove the hill giants from that area just because some goofballs decided to go there at level 1 despite my warnings. There are really places you shouldn't got at lower levels. Probably not smart to go through a portal to the lower planes or journey to a dragon graveyard, for example.

I know, right? "Ok, well what's in that mausoleum?"

"A powerful Lich left over from when the undead horde descended on our lands 100 years ago. Some of the country's best adventurers have tried to assail that place and failed."

"All right guys! Let's go."

They were level 10. They suicided into an illusion shielding a prismatic wall. Entire party. What do they do upon forming new characters? "Lets take out the mausoleum." They got repeatedly crushed. And the monsters they managed to slay? Were all planar binding.

[Nifft]

I'm struggling with a conundrum: My players, each level 6, are about to go to a region with these qualities:
20% normal magic, 50% wild magic, 30% dead magic
No Gravity or objective directional gravity, depending on where you are.
Floating rocks, some the size beach balls, some the size of houses...
Wildly fluctuating temperatures...

This region was the battle ground for a massive exchange between two magocratic empires, and has never recovered.

What monsters could they find here? How do I provide a reasonable, but not overbearing challenge for my players, while also giving the area justice for how dangerous it is supposed to be (it is the single thing that a gold dragon in my setting is afraid of).

You know what kind of "fun" you can find on old battlefields?

Unexploded munitions.

Maybe there are living spells which seek out powerful spellcasters (including but not limited to dragons).

Maybe there are some mage-seeking drones which currently just flutter around the Wild Magic area, since that's where spells spontaneously happen, and try to decapitate illusory spellcasters until a real one shows up. When any PC casts a spell, one of the drones swoops down and forces a Reflex save (Dragons dislike this) or deals Dexterity damage (Dragons hate this!) and explodes one of the caster's highest remaining spells or spell slots.

Maybe there's a red War Golem (or an Epic Colossus) which mistakes one of the PCs for its commanding officer. But then an equally broken blue War Golem makes the same mistake and attacks the first War Golem, to get at "the general".

Maybe there's a contingent forcecage spell-trap which also imposes an anti-magic field, and is sized for a dragon -- the PCs can squeeze through the bars, but the gold dragon would be screwed.

A contingent wall of force might be a nasty hazard against a battalion of charging dragon-knights, but against a party of walking PCs it's just a minor face-bonking inconvenience.

[RSGA]

I know, right? "Ok, well what's in that mausoleum?"

"A powerful Lich left over from when the undead horde descended on our lands 100 years ago. Some of the country's best adventurers have tried to assail that place and failed."

"All right guys! Let's go."

They were level 10. They suicided into an illusion shielding a prismatic wall. Entire party. What do they do upon forming new characters? "Lets take out the mausoleum." They got repeatedly crushed. And the monsters they managed to slay? Were all planar binding.

At least that's a few dead hopefully evil outsiders. Wall's nasty though.

[Calthropstu]

At least that's a few dead hopefully evil outsiders. Wall's nasty though.

Yeah, I know. I had that place very well flushed out long before the campaign even started. One of my players was incredibly impressed. He told me "That's the first time I've ever seen someone play a lich who has survived for hundreds of years right." The "headway" they were making was marginal at best. He used planar binding to get a feel for what they could do. They only fought him once and that was finally enough for them to say "nope" and finally get back to the plot.

[Fizban]

This region was the battle ground for a massive exchange between two magocratic empires, and has never recovered.

It occurs to me that you might need to define your expectations of this exchange, in order to properly detail the area. Because as common as the fluff is, that's not how magic actually works in dnd. Which means that unless the DM rules that x+y+etc= normally impossible effects, it doesn't happen. So, what do you say creates a wild magic zone, dead magic zone, warped gravity zone, etc?

The problem is that if you're thinking something like "magic nukes," well nukes aren't lobbed back and forth at a particular battlefield. Artillery is lobbed at enemy positions, but said positions are targetable and exist specifically because they provide protection against a certain amount of artillery. Depending on the battle, sometimes sustained bombardment can destroy a position, sometimes it fails utterly, and sometimes it fails to damage the position but shellshock makes the assault much easier.

A magic shell that instantly causes permanent wild/dead/grav alterations would not require a massive exchange, so it's not a nuke, and you need a type of war that involves "massive exchanges." Fortifications, infantry, artillery, armored vehicles, etc. This indicates a particular type of magitech setting which you may or may not have intended.

I'm struggling with a conundrum: My players, each level 6, are about to go to a region with these qualities:
20% normal magic, 50% wild magic, 30% dead magic
No Gravity or objective directional gravity, depending on where you are.
Floating rocks, some the size beach balls, some the size of houses...

As long as spellcasters can tell if they're in an altered magic zone and the party is never forced to fight in bad conditions, these are all just window dressing with little or no inherent danger- unless said objective gravity is something like straight up or 200+ feet into a cliffside, and the floating rocks aren't so much floating as actively storming. The point being, either its obviously lethal, obviously not, or an effective trap that you simply not have the PCs encounter (or make obvious through other clues). Note that even without being within a dedicated dead magic area, the DM can easily say that the energy of the place prevents teleportation, which I would expect to make any high level anything skittish.

Wildly fluctuating temperatures...

Nor is this any real danger thanks to Endure Elements, unless by temperature you mean Elemental Plane of Fire/Cold levels of damage, which at 3d10 is still easily blunted or negated with 2nd level Resist Energy. Unless you're talking like the rain of random fireballs on Avernus or other "you randomly take 10-20d6 damage" such that you need both fire and cold immunity to safely enter, or frequent enough at lower damages that you need a continuous item of multiple energy types to stay for any duration.

What monsters could they find here? How do I provide a reasonable, but not overbearing challenge for my players, while also giving the area justice for how dangerous it is supposed to be (it is the single thing that a gold dragon in my setting is afraid of).

Living Spells have been suggested multiple times, basically because they're the only actual published support for the idea of excessive magic causing wibbly things. They're also a "template" monster with their actual power determined entirely by what spell you use, how OP that spell is, and how it interacts with the template. It does allow you to perform some specific environmental storytelling, as once they know what spell it is, they know that's a spell or effect that was used frequently. And some spells are so broken (especially if you take some liberties in their combination) that you could definitely make something a dragon is afraid of (yet moreso if they say, get to ignore the dead magic because reasons).

As for monsters- well that's kinda the problem isn't it. Because there's no reason for there to be big nasties hiding in the nasty terrain. There's no prey (unless they raid out, which would be a significant local problem), and they need immunity/regeneration to any significant problems to live there. But if there are sources of perpetual arcane energy in the area, that's a food source for monsters that eat magic. Aoa (Fiend Folio), Arcane Ooze (MM3), Spelleater (Dragon Magic), Balhannoth (MM4), Disenchanter (Fiend Folio), and so on. And there are elementals, whether generated or called and abandoned, including the Elementites (Planar Handbook) Storm (MM3), Omni (MM3), and the Tempest (MM2), all suitable if the place is shot through with energy storms, and which could be fluffed as not leaving the area due to liking it there and/or the area being ringed with dead magic that they don't want to enter (which could have been laid down to contain the fallout from the battle). Energons (Manual of the Planes and Planar Handbook) and the Thunder Worm (Fiend Folio) are incorporeal elemental creatures that physically can't pass through a dead magic perimeter. Chaos Beasts and Unravelers (Planar Handbook) are not appropriate for 6th level characters, but are body dissolving ultra chaos/law things if you want a "wild magic" creature.

Of these, the Aoa droplet, Energons, and appropriately sized elementals can be fought by 6th level PCs

There's also the possibility of leftover golems or other constructs, which if they can be usurped would provide a reason for people to consider going in (Eberron has ways). A stable of clockwork steeds leftover from a mounted company would be a useful find. But this is really only if both sides were suddenly wiped out, otherwise they'd take their golems back with them.

Magically backed trenches and fortifications are likely to have any trap spell, such as Fire Trap, Glyph of Warding, Explosive Runes, or Symbol, or Sign of Sealing (SpC). For a twist, a Living Glyph of Warding is a heck of a thing to have wandering about. A living Cure spell is also appropriate for obvious reasons, if not actually killing the PCs.

[King of Nowhere]

I had something very similar in my world, and I solved this by saying that your very soul alters the place. and being high level impacts your soul. so, basically, the higher level you are, the stronger encounters you get, for in-world reasons. although the place is still less deadly for a high level party.

also, i can suggest random body horror caused by the wild magic. have everyone roll fortitude at evening, whoever rolls lowest the next day has an abscess in their back that seems resistant to magical healing. if one tries to cut into it, a little tentacle strikes out. the whole thing doesn't do much mechanically - it's easy enough to cut away the tentacle, and then a cure light wounds will fix the damage - but it should squik the players, and it should make them realize, viscerally, that this is a place you don't want to be in. You can see why a gold dragon would be afraid of it.