Gimmick Boss

[Yasahiro]

So I have a question.

What you guys think about usage of gimmick bosses? Like, you need to say you target a thing on the creature in order to inflict damage. While no such thing exists by RAW, would you be furious or accepting or such if a GM did it to you?

Hell, things like "Use this" or "Hit it there" or even something like the most anime thing "Expose the core, kill the core", with the creature you were fighting actually being a shell and "killing" it just leaves a core which you must destroy, either in any way or using something specific, in order to stop it from coming back? It would require the DM making rules for targetting specific places, but what would you think about it?

And yes, if some people get the "Knights of Sidonia" vibe, it might be. Or "Evangelion"

TL;DR:
What you think about "Do this to a creature or it comes back/still fights"

[Vhaidara]

I generally don't like bosses where the gimmick is binary (you have to use this to hurt it). I prefer gimmicks of environment. My personal favorite was a boss who got a free bull rush when she hit you, and the party fought her in an arena full of flaming geysers.

Another fight i have planned is on a 10x10 grid. A few times a round (Initiative counts 20, 10, and 0), random elemental effects will occur, because you're fighting someone in the middle of a battle of elemental lords. Examples include a wave washing over the battlefield (1d10 for size, 1d4 for direction, 1d10 for center point, 1d10 for distance, treated as a bull rush), a seismic shockwave (1d100 for center point, 1d10 for radius, Reflex or be knocked prone), etc.

Basically, battlefield gimmicks, especially ones that can work for or against the party, are much more memorable than needing the +2 Spoly Hammer of Smititude to damage the boss.

[DrMotives]

Targeting specific body parts was a thing in 2e, and while I kinda miss it as a player, I can see why it wasn't included in 3.x . It took a -4 penalty to target a big part like a limb or torso, and -8 for a specific small part like an eye. And natural 20s were automatic hits. So every low level character who felt they'd miss most of the time, always took called shots. And very high level characters who'd still hit with the penalties, always took called shots. Combat wound up being a bunch of dudes only ever injuring their opponents heads, for the extra effects it had. Except for mages of course, they didn't use called shots, they just dominated things with magic.

[Yasahiro]

I generally don't like bosses where the gimmick is binary (you have to use this to hurt it). I prefer gimmicks of environment. My personal favorite was a boss who got a free bull rush when she hit you, and the party fought her in an arena full of flaming geysers.

Another fight i have planned is on a 10x10 grid. A few times a round (Initiative counts 20, 10, and 0), random elemental effects will occur, because you're fighting someone in the middle of a battle of elemental lords. Examples include a wave washing over the battlefield (1d10 for size, 1d4 for direction, 1d10 for center point, 1d10 for distance, treated as a bull rush), a seismic shockwave (1d100 for center point, 1d10 for radius, Reflex or be knocked prone), etc.

Basically, battlefield gimmicks, especially ones that can work for or against the party, are much more memorable than needing the +2 Spoly Hammer of Smititude to damage the boss.

What if the boss instead has multiple phases, or that you have to utilize environment in his second phase or it restores itself to first phase?

I am probably explaining things bad.

[crunchykoolaid]

I've tried things like this before, and it was both good and bad.

For example, I had the party fighting inside a giant forge that was just starting up after thousands of years. At certain points in the fight, the fire below them would flare up, turning parts of the room into hazards and such. At first, the party just felt I was trying to add artificial difficulty due to the extra fire damage.

Once they got the pattern down, however, they began using the fire bursts as impromptu cover, working their way behind the boss and surprising it, cornering it so the next burst roasted it crisp.

So basically, it all depends on your players. As long as you think they can be imaginative enough to use the gimmicks to their advantage, go ahead as long as you're not just trying to add extra difficulty to a fight.

[Vaz]

There is a set of armour within the Book of Vile Darkness which has chains attached to 4 people; whenever the dude in the armour takes damage, that is split over 4 people.

There is also the Shared Pain trick which is similar.

[TheifofZ]

Artificial difficulty ala Legend of 'strike the weak point and then hit it with the sword 3 to 4 times' Zelda as a gimmick isn't something I think would be enjoyable in D&D, but some gimmicks can make for awesome fights.
I think the most fun I've had in a boss fight is one that took place at the top of a giant tower, and the GM intended him to escape by jumping off and vanishing.
I said 'screw that', and jumped after. The mid-air boss fight that took place while falling to our potential deaths because of that was amazingly fun.
So, you know. If you must use gimmicks, consider instead environmental effects or events that change the way players have to think about the battle.

The best gimmicks are things that can be used by both the boss and the party to change the situation, and require creative play by the party to use to their advantage.

[Vaz]

In Final Fantasy X, there was a boss who had 4 discs which would rotate and change to display a symbol. Each symbol would increase his power casting spells of that particular element, becoming especially powerful if all four matched. You could help change the circle by directing attacks at that rather than the boss.

[TheifofZ]

In Final Fantasy X, there was a boss who had 4 discs which would rotate and change to display a symbol. Each symbol would increase his power casting spells of that particular element, becoming especially powerful if all four matched. You could help change the circle by directing attacks at that rather than the boss.

If we're really going to dig into video games for actual examples of gimmicky awesome boss fights, then I'll need time to really dig out my tome of lore, as it were.
But those are more difficult to port over, because the action in video games is rarely as 'set' as it is in D&D.

[Red Fel]

What if the boss instead has multiple phases, or that you have to utilize environment in his second phase or it restores itself to first phase?

I am probably explaining things bad.

This still raises Keledrath's concern, with which I agree. Any boss encounter that goes "If you don't do X, you cannot win," (except where X is "deal HP damage to the boss," because duh, let's not be pedantic here) is a binary gimmick, and sucks if you are unaware of the gimmick or unable to trigger it.

"Use the environmental hazards in the second phase or it goes back into its first phase" is like "Strike the heart with a silver arrow" or "Recite the words of sealing" or "Hop on one foot dangling a pufferfish while repeating yu mo gui gwai fai di zao." If the PCs don't know the trick, or can't use it, they lose, full stop. And that plays like a "Gotcha" on the part of the DM, whether intended or not. And that's terrible.

A better option, in my mind, isn't to make the boss exclusively vulnerable to the gimmick, but additionally vulnerable to it. For example, rather than having the boss only killable if you drive a stick of gopher wood into its heart, the stick of gopher wood is super effective, while regular methods still have ordinary (or slightly reduced) effectiveness. This rewards the prepared or informed PCs, while not punishing those who missed the clues (assuming you ever gave them clues).

Crunchykoolaid offers a prime example of this. The environmental hazards could be weaponized to make defeating the boss both easier and more engaging, rather than a mandatory "push this button to win the game" event.

[Taveena]

The one gimmick fight I've been in was... literally the Netherspite fight from WoW. Portals blasted beams at the boss, buffing him. You could block them, preventing him from getting the buff, but debuffing yourself in the process.

So we did. Yay for videogame knowledge.

[prufock]

Like most things, gimmick bosses can be done well or done poorly. I tend to like environmental effects, as Keledrath suggested, but those aren't so much gimmicky bosses as just additional hazards.

I have no problem with "phases" of a boss fight, provided they are logical and not just a new HP bucket. Gimmicky fights shouldn't be true/false, they should be multiple choice.

For example, I ran an end game where there was a BBEG with his crew trying to raise a dragon from the dead (in this setting dragons were rare). So the PCs show up at this pit dug in the desert, in which the dragon skeleton sat, with the BBEG and guards. The guards attack while the BBEG performs the ritual to bring the dragon to life. Meanwhile, his cleric second-in-command finishes animating the dragon skeleton.

If the PCs stop the ritual, they still have to fight the skeleton dragon, mooks, BBEG, and second.
bies.
If they don't, they no longer have to fight the BBEG, mooks, or second (because the newly risen dragon will kill them - the PCs don't know that), but have the much tougher dragon to fight.

The dragon is reborn slowly, growing flesh over the bone round by round for one minute. This created an interesting dynamic, with the most dangerous enemy getting MORE dangerous over the course of the battle.

[yellowrocket]

"Hop on one foot dangling a pufferfish while repeating*yu mo gui gwai fai di zao."

But uncle. . .

[Deadline]

There are already tons of "gimmick" monsters in D&D, so if it's done along those lines, it'll probably be ok. Things with regeneration, like Trolls (you need acid or fire to kill them), things that use spells or abilities to extend the punishment they can take (share pain, shield other), or worse yet, things that HP damage can't kill (like a Frenzied Berserker).

[rockdeworld]

While no such thing exists by RAW,
I beg (http://www.d20srd.org/srd/monsters/hydra.htm) to differ (http://www.d20srd.org/srd/monsters/lich.htm)... (and for some other examples of puzzle monsters/bosses: rust monster (http://www.d20srd.org/srd/monsters/rustMonster.htm), hellwasp swarm (http://www.d20srd.org/srd/monsters/swarm.htm#hellwaspSwarm), ochre jelly (http://www.d20srd.org/srd/monsters/ooze.htm#ochreJelly), tarrasque (http://www.d20srd.org/srd/monsters/tarrasque.htm), gorgon (http://www.d20srd.org/srd/monsters/gorgon.htm), medusa (http://www.d20srd.org/srd/monsters/medusa.htm), phase spider (http://www.d20srd.org/srd/monsters/phaseSpider.htm))


What you think about "Do this to a creature or it comes back/still fights"
I have no strong feelings one way or the other, so long as it's clear to the PCs what they need to do to fight it (or they can find out easily using their regular methods). Otherwise I think they're just annoying, frustrating and especially not fun.

[Douglas]

A better option, in my mind, isn't to make the boss exclusively vulnerable to the gimmick, but additionally vulnerable to it. For example, rather than having the boss only killable if you drive a stick of gopher wood into its heart, the stick of gopher wood is super effective, while regular methods still have ordinary (or slightly reduced) effectiveness. This rewards the prepared or informed PCs, while not punishing those who missed the clues (assuming you ever gave them clues).
I was once in a power gaming dungeon crawl called the Cheese Grinder at DragonCon. One of the rooms (selected at random) that I played through featured a boss inspired by the bunny of doom from Monty Python and the Holy Grail. We could fight it conventionally, just with great difficulty given its build - it could spend move-action movement on teleporting and split the movement around its attacks, had a very high movement speed, had a vorpal bite, and had very high AC and saves, among other things, and abused it all as thoroughly as a PC might. Then someone decided to try completing the obvious reference by calling out "bring forth the Holy Hand Grenade of Antioch!" We were then treated to an automatic cutscene victory.:smallbiggrin:

[Urpriest]

Gimmicks in general are ok, but you should make sure they draw from the rules, rather than bypassing them. Video game gimmicks are almost never a good idea because the only reason they were fun in the games they came from is because they had interesting connections to the mechanics of those games. Take that away and you're left with an immersion-breaking reference.

[Orderic]

Gimmicks can be fun. After all, several interesting enemies have them. Kill the troll with fire or acid, burn the stumps of a hydras heads, etc. However, the gimmicks have to be interesting and something, that the players can actually influence.

One of the most memorable fights in my campaign was against a giant block of stone. Which had a very annoying ray that dealt dexterity damage. However, what truly mad this fight interesting was an ability of the stone that gave it a few temporary HP at the start of its turn, as well as a massive defensive buff - which went away if the temporary HP were lost. This caused my players to eventually adapt their strategy and attack in a way that ignored its AC.
In a recent session they fought four constructs who shared a health pool, which caused them to use AoE damage, which dealt damage once for each affected creature.

Both of these fights were interesting, not because they had gimmicks, but because the actions of the players could heavily influence the fight and required them to use a strategy tailored to the enemy.
One more thing, that is important about these gimmicks is, that they were easy to spot. Tho stone had an aura of light while its defensive buffs were up, while I allowed a spot check to realize that the constructs were sharing damage. Had there been no clues like these, my players would probably have thought I was changing things at will, screwing them over and hated me.

TLDR: Make gimmicks fun, interesting, something the characters can interact with and make absolutely sure that the players will realize what is going on.

[Elder_Basilisk]

Gimmicks in general are ok, but you should make sure they draw from the rules, rather than bypassing them. Video game gimmicks are almost never a good idea because the only reason they were fun in the games they came from is because they had interesting connections to the mechanics of those games. Take that away and you're left with an immersion-breaking reference.

The other consideration with video game gimmicks is that video games often scale the difficulty with th expectation that you will have to load and restart several times in order to win. In fact, a lot of players expect to need to save/load; if they don't have to, the game is too easy. With a gimmick fight or puzzle, you can build your knowledge of the situation and figure out the gimmick through those multiple attempts. In fact, that may be expected.

In a tabletop roleplaying game, it is typically one run through, win or lose. Most players frown on doing a save/load style reset. That means that the gimmick needs to be something that can be figured out in course of the battle without save/loading and will generally mean that it has to be less complex than a video game gimmick.

That said, I agree wholeheartedly with the idea that the gimmick needs to be connected to the mechanics of the game. If they're not, you risk breaking immersion or worse yet facilitating failure because players are trying to accomplish their task within the rules of the game while the gimmick requires the players to do something entirely outside those rules.

[TheifofZ]

The general gist that everyone seems to agree on is gimmick boss fights need to have a few specific points, or else they're no good.

The fight can't be a binary 'do this or lose'. Any special weakness should be an option that rewards the players for working to discover it, not something they're required to know about if they want a chance to win.
The fight should use rules in D&D, not necessarily ideas from video games. Video games have a lot of mechanical advantages for gimmicky fights that players in D&D don't have: The ability to load a save, explicit expected abilities, and so on.
The fight should reward creative or tactical play, rather than forcing it. If the party has a wide variety of ways they can approach the fight, it can be more fun and interesting to creatively use available options in ways that weren't expected, rather than just using them in a linear 'do this, now do this' method. This does feed back into the first point as well: Binary Yes/No fights are boring.

[rockdeworld]

The fight can't be a binary 'do this or lose'. Any special weakness should be an option that rewards the players for working to discover it, not something they're required to know about if they want a chance to win.

No, I'd say that's ok, provided it's clear what the PCs are supposed to do. Eg. if the boss is "drop the gate on its head, then fire the seige crossbow at it" with the challenge being to get to the gate controls and then the crossbow, it's still a battle where the PCs can be awesome.

[Red Fel]

No, I'd say that's ok, provided it's clear what the PCs are supposed to do. Eg. if the boss is "drop the gate on its head, then fire the seige crossbow at it" with the challenge being to get to the gate controls and then the crossbow, it's still a battle where the PCs can be awesome.

Can you give me an example of a scenario where that doesn't feel forced?

That's the point. It's not just a case of "the players have to know and be able to do this or they lose." Even if they know it, they may not be able to do it; even if they can do it, the fact that it's the only way threatens immersion.

It's one thing in the case of creatures like Liches, where there's only one way to destroy them permanently, but any number of ways to defeat them for the moment. But when you explicitly tell the PCs - or worse, the players - "this is how to win the encounter," it doesn't matter that the challenge is in accomplishing it. It matters that you've turned combat from an engaging encounter rewarding creativity and tactics into an exercise in button-pushing.

In your example, if they come up with the idea to drop the gate on the creature then fire a siege weapon down its throat, that's awesome. If they have to do that in order to win, and they don't know it, that's horrible. But the middle-ground you've described - telling the PCs that they have to do this in order to win - just makes it feel forced. It's not nearly as awesome as it would be if they'd figured it out on their own, and it's not a solution that's sufficiently obvious that they could piece it together on their own. Telling them takes the innovation and creativity out of it.

[TheifofZ]

No, I'd say that's ok, provided it's clear what the PCs are supposed to do. Eg. if the boss is "drop the gate on its head, then fire the seige crossbow at it" with the challenge being to get to the gate controls and then the crossbow, it's still a battle where the PCs can be awesome.
Tell me, do you also like it when your party has little wheels on their feet to make it easier for you to keep them on the railroad?
Because that's what that is. Sure, the desperate struggle to push the button might be intense, but it's not interesting or challenging except in the difficulty of getting to the button. And that's not okay in a boss fight. Puzzle bosses with clear labels are boring, and puzzle bosses when I don't even know that I'm playing, say, Jenga instead of Mahjong are just plain old bad.

I'd rather, sticking with your given scenario, be able to defeat the boss without dropping the gate on it, or firing the siege crossbow at it.
But if I can lure it into the gate and drop the gate on it, having the beast stunned rewards me by giving me time to bash at it, but isn't something I have to do to win.

Using time honored classics, the Zelda game's boss fights are all terrible. The challenge is in not dying, and following the tour guide.
Oh, look. A giant target. I shoot it with an arrow because nothing else works. Now I smash it with a sword. Now I repeat.
That's really friggen boring, and unfun.

[SkipSandwich]

A lot of 'gimmick battles' can be made just by smart paring of creatures together

"Of Lizards and Flesh Golems"
A Flesh Golem stands guard over a Shocker Lizard colony, attacking the golem alarms the lizards into using their Lethal Shock ability (which heals the golem), and if the golem sees anyone attack the lizards, it immediately goes berserk and will rush the attacker. The first time the golem rages it triggers a Programed Image spell by its creator that causes it to calm down, but there will be nothing stopping again should the players provoke it a second time. The golem holds a key that unlocks the gate to the next area (as seen hanging from a chain around its neck).

The lizards are skittish, and will use their non-lethal shock and run rather then engage the players unless cornered, at which point they use their Lethal Shock.

Players can A) ignore the lizards and just focus-fire the golem down if they have enough damage potential and/or electricity resistance to outpace the healing from the lizards, once the golem is down the lizards should be easy to scare off or kill individually

B) use stealth to sneak around the golem and corral/kill the lizards before engaging, alternatively, the party can use ranged attacks to pick off the lizards from cover

C) intentionally provoke the golem into a rage and lure it away from the gate, then sunder/pick the lock and leave w/o engaging

ect...

[rockdeworld]

Can you give me an example of a scenario where that doesn't feel forced?
I don't know what you mean by "forced" in this context. If the example I gave is forcing it, then no. And I don't care, because I think it's an example of a good encounter (once per campaign or so). Like I said, the challenge for the PCs would be getting to the gate controls and necessary weapon, such as by getting around traps or enemies. It's just like PCs do in the rest of a campaign, except while taking fire from a more powerful monster (though presumably with plenty of places to take cover), and it's the kind of encounter that people can remember as epic, even if it wasn't their spells/attacks that finished the enemy off. If you dislike that kind of encounter, we have a difference of opinion.

[ericgrau]

No encounter should ever have an all or nothing solution. Ever. It's boring and uncreative, whatever you may think of it. And when forced on the players it can only be a frustrating waste of an evening. No amount of smarts or creativity will find The One Answer. Either you spoon-feed it to them or they may make wild guesses. Because there is only 1 answer, it must not follow normal game rules of reality because normal game rules allow multiple answers. Thus there is no way to know it and the challenge is not solvable by conventional means. So any clues are basically neon signs, which again either spoon-feed the answer or aren't enough information to find the answer at all no matter how smart or creative the players are. Sometimes pure luck might work. And if you fool them you aren't outsmarting them or being a clever DM, you're only wasting their time with the impossible (barring blind luck). The only good way to do this is not to do it at all. It's actually a crutch for when the DM isn't creative enough to think of a creative encounter.

Messing with the terrain or giving the boss cool toys is fun. Traps or other mechanisms in the middle of the battlefield are neat. As long as nothing is all powerful at what it does and as long as you don't give it a super weakness.


I don't know what you mean by "forced" in this context. If the example I gave is forcing it, then no. And I don't care, because I think it's an example of a good encounter (once per campaign or so). Like I said, the challenge for the PCs would be getting to the gate controls and necessary weapon, such as by getting around traps or enemies. It's just like PCs do in the rest of a campaign, except while taking fire from a more powerful monster (though presumably with plenty of places to take cover), and it's the kind of encounter that people can remember as epic, even if it wasn't their spells/attacks that finished the enemy off. If you dislike that kind of encounter, we have a difference of opinion.

As for a spoonfed solution with multiple ways to reach it... that's more like a mini-game. I guess that's alright. It's party not D&D anymore, but partly still is. Without a 1,000 hours of playtesting the mini-game is by necessity simple. But hey checkers can be fun too, and checkers where you can cast fly is a little more fun.

[AlanBruce]

I ran a gimmick encounter awhile back, but I allowed the players several choices on how to deal with the boss.

The party was around levels 10-11:

DMM Cleric/Prestige Paladin/Inquisitor

Beguiler

Paladin of Freedom/wizard/Abj. Champ

Necromancer

Conjurer

Dragon Shaman

Petal Bard

The scenario: The party trekked through an ancient sylvan forest in order to stop a dry lich who had allied itself with a mad druid and were destroying the forest. The Petal knew that the 'wisest and oldest spirit in the forest would provide guidance on how to deal with those two'.

The oldest spirit here was a very big and very old treant (Gargantuan in size).

They reach his sacred grove- a dome made of tangled roots- and are greeted by him and a pair of animated trees. The Petal talks to him and the party starts to watch quite warily as the two animated trees begin to block the entrance to the domed grove, preventing their escape.

Then, after some ominous remarks from the treant (and the successful roll of Arcana, Nature & Religion checks), they learn that the dry lich met the treant days earlier and subjected him to a horrific ritual turning him into a special type of necromental.

The fight begins and the conjurer disposes of the animated trees easily through judicious use of Blast of Flame.

The treant starts beating the melees down hard... until the beguiler notices four thick roots coming out of its back and tangled on the dome's ceiling, connected to some amber cocoons, knotted by the roots above and held tight.

Whatever was in those four cocoons, was giving the beast unholy strength and vitality (fast healing). Again, through successful rolls on the party's behalf, they learn that the treant can be taken down in power considerably if they sever the cocoons from the treant, but the roots are thick and it would take a few rounds to break them.

The solution? Turn him, like any undead. This caused the treant to become staggered and kneel, causing the cocoons to drop down a few feet.

Cue in the casters who would fly up and begin slicing the cocoons open and freeing four dryads sent days earlier for the same exact reason.

Every time a dryad (or two, since there were two casters above) would be freed (and unconscious), the treant would stand up and the remaining cocoons would become knotted again on the roof.

Rinse and repeat.

Could the party kill the treant without using that method? Yes. They had the firepower and melee power to hack the thing down, but because they identified the people inside, they chose to rescue them, extending the battle for almost a minute, if not more.

As a result, they gained valuable information from the very weakened dryads and made new allies. I haven't had a gimmick fight since, because now the party has a lot more resources at their disposal, but it was an exercise in using their resources creatively.

[Yasahiro]

...I feel dumb after only now remembering about Lich Phylacteries.

So the general consensus is, gimmick bosses are okay but only if it is related to environment OR if it is just an easier way of doing it, but there are still other ways of accomplishing the task of beating this thing?

[SkipSandwich]

...I feel dumb after only now remembering about Lich Phylacteries.

So the general consensus is, gimmick bosses are okay but only if it is related to environment OR if it is just an easier way of doing it, but there are still other ways of accomplishing the task of beating this thing?

I believe the rule of thumb is that complex encounters should be designed so that there are least 3 different ways to "solve" them. I personally assume players will use either;
A) Brute Force - The PC more-or-less ignore any puzzle or strategy in favor of smashing the problem via straight combat

B) Strategy - The PC's figure out the rules/tactics the opponents are using and then exploit/overcome them to minimize the risk and resources expended

C) Third Option - The PC's figure out a way to bypass the encounter without resorting to combat.

[Milo v3]

My entry to Paizo's stat up an occult Rasputin competition was a gimmick boss, whenever you killed him he comes back to life with different stats.

[Red Fel]

...I feel dumb after only now remembering about Lich Phylacteries.

So the general consensus is, gimmick bosses are okay but only if it is related to environment OR if it is just an easier way of doing it, but there are still other ways of accomplishing the task of beating this thing?

Pretty much.

Gimmicks should be things that the PCs can come up with and feel awesome about, not things that you force on them. They should be things that make an encounter more engaging and entertaining, not "push this button to win" requirements. The goal is to encourage and reward innovative and smart play, not to force everyone to think and operate like the DM does.

[Spore]

Last time my DM made a gimmick boss I loved it to pieces. I suggest the gimmick gives you a fair advantage rather than an instant win.

My DM made an adult red dragon vulnerable to fire after giving us a Staff of the Dragon. Naturally my character chose to use the staff on him and let the (fire resistant) Dwarven Barbarian ride on his back. The breath weapon and the insane damage of the barbarian made quick work of the otherwise complicated fight.

[Yasahiro]

Though, to be fair, it also depends on how it is implemented.

As example, Knights of Sidonia, a somewhat new anime, has these extraterrestial creatures, Gauna, whose Main body has to be destroyed in order to stop them from regenerating. Said Main Body can only be pierced by a specific objects, which they had limited amount of but later replicated. It took time for the thing to regenerate so they could get rid of it for quite a bit if they stripped of all the "Placenta"(The parts of body it regenerates)

Now, I know how stuff happens in Anime and how it works out in a game is different, but let's look at it from this angle:

How did people feel in that anime before they found a way to pierce the Main Body? That would be what players would feel like. It's like making Lich's phylactery that is only susceptible to a specific material. It is possible to just strip away the "placenta" constantly, but it takes time and everyone has to be careful. But the most important thing is the Fear. Because until they find a way to kill it, they are afraid. It's like fighting Juggernaut.

But even in this situation there are many ways to deal with it. One would be finding that method to pierce its main body, the other would be to just continue weakening it and stripping away the placenta, another would be to escape, try to avoid it.

Technically, there IS a D&D monster that works in such way. It's Zargon, from Elder Evils. He will regrow in matter of days until the horn is destroyed and there is only one way to destroy the horn.

[Silvrfox]

Its not just lich phylacteries. Damage reduction is a build in gimmick of the game really. Attack normally for reduced effect, or use kryptonite to kill it faster. Knowledge checks give TYPICAL gimmicks (damage reduction, special attacks, etc) but a real way to throw them for a loop is like the red dragon example above. When you assume what you "know" is correct without fact checking it on whats, you know, happening, then the players, like anyone who fights mythical beings as a 9 to 5, need to be on their toes.

[Red Fel]

It's like making Lich's phylactery that is only susceptible to a specific material. It is possible to just strip away the "placenta" constantly, but it takes time and everyone has to be careful. But the most important thing is the Fear. Because until they find a way to kill it, they are afraid. It's like fighting Juggernaut.

But even in this situation there are many ways to deal with it. One would be finding that method to pierce its main body, the other would be to just continue weakening it and stripping away the placenta, another would be to escape, try to avoid it.

Technically, there IS a D&D monster that works in such way. It's Zargon, from Elder Evils. He will regrow in matter of days until the horn is destroyed and there is only one way to destroy the horn.

Let's be fair, though. Liches, Elder Evils, and similar "There is only one way to destroy this foe" enemies are fairly epic encounters. I don't just mean epic levels, I mean epic. A Lich is supposed to be a spellcaster of unspeakable power who has unnaturally preserved his existence through truly vile means. He is Lord Voldemort, he is the devious and recurring foe, he is incredibly dangerous, and he is an awesome BBEG candidate. Facing a Lich should be a suitably epic and awesome encounter (or series of encounters, or campaign capstone).

The Tarrasque is another example - it's divinely protected, and must be killed and then Wished down. It's designed to be a unique and terrifying encounter, the kaiju of the D&D world. (The fact that we've optimized anti-Tarrasque parties to Celestia and back notwithstanding.)

Similarly, Elder Evils are beings of unspeakable power, whose very presence marks the End of All Things. Their very existence is antithetical to the Material Plane, and they represent power so awesome that even the gods can't face it directly. It makes sense that a being like this should be uniquely difficult to kill.

But there are tiers of enemies below them. There are Outsiders and Dragons, who are powerful and intelligent, but still killable. There are mortal races, like exceptionally strong Orcs or Goblins or Elves. There are mooks, like Kobolds. And taking anything short of a suitably epic foe and making it killable in only one way just feels forced. Even your typical BBEG ought to have more than one option. (Again, remember that the Lich can still be stopped by various means, even though only one permanently kills him.)

That's the point. Anything short of an incredibly epic foe should be a fight with options. With the exception of Elder Evils - where, really, the whole concept is that most beings are powerless to stop them - you should be able to put a boss down in a meaningful way, even if it's ultimately temporary, without resorting to a single and uniquely specific method.

[Telonius]

I have nothing useful to add to the conversation - just wanted to note that I was wondering if somebody was trying to stat up this guy as a BBEG. (I'd say Artificer 20 if you're doing that).
http://s.ecrater.com/stores/8993/54776329a0028_8993b.jpg