Is the CR system completly Borked for most monsters?

[Zancloufer]

So upon reviewing the CR advancement rules for monster to respond to a different thread on Giant Octopus, I realized that it is REALLY borked.

IE: A Colossal Fiendish Octopus (HD of about ~26) would be about CR 19? (8+2 for Fiendish +3 for 3 size increases +6 for 18 more HD). Now said creature would have an AC of about 22 (18 Base + 12 for Nat armour for size -2 for Dex reduction - 7 for size) which would be an awesome touch AC of 3. Now it does have DR/This doesn't matter at CR 19, and SR of 31 (that would actually do something, like a 50% spell failure though their are ways around it). Of course it's 8 attacks at +21 to hit for 1d4+11 damage would mean it could actually hit stuff a number of times per round, though it would really tickle them and any DR would really hurt it's damage output. It's 26d8+182 HP (about ~300 on average) would make it a decent roadblock, if full BAB classes couldn't auto-hit it, even if power attacking for half their BaB. Not to mention said BAB classes by that point are putting out 100-200 damage Full attacks without trying, or even one shotting it with a crit on a maneuver.

What I'm saying is this monster would "Challenge" a level 19 party. Now I know that any level of theoretical optimization would make said Int 3 Octopus a one-shot with a level 2 spell. Even if the party isn't prepared, how is this monster a challenge to a standard level 19 party? Am I looking at it wrong not using it's strengths right, or are their some real problems with how the CR system scales for most creature types?

[Psyren]

For MOST monsters? No - it's still a useful starting point, you just have to take it with a grain of salt.

It's still better than having to read every monster's stat block in-depth and compare it to every other one before building a single encounter.

[Blackhawk748]

Well, i agree with you on most of your points, the CR system is a bit dumb. Were creatures are a good example, if you have a silver weapon they become almost a joke.

Now for the octopus, remember it swims. Now at lvl 19 that isnt as big of a deal as it used to be, but think about it, they dont have to be next to the water for this thing to explode out and start snatching people. Think Watcher in the Water from LOTR and you get a pretty good idea of how it should fight.


The fight should go like this

Surprise Round: Grapple Mage
Round 1:Grapple Beatstick (or second Mage)
Round 2:Grapple second Beatstick (or first if there was another mage)
continue repeating until party is dead or runs.


Remember grappling is an often overlooked form of attack

[Psyren]

Surprise Round: Grapple Mage
Round 1:Grapple Beatstick (or second Mage)
Round 2:Grapple second Beatstick (or first if there was another mage)
continue repeating until party is dead or runs.

At level 19, Mage 1 should have either a contingency, Freedom of Movement or Heart of Water up at all times. And that's if he's even really there. (http://www.d20srd.org/srd/spells/astralProjection.htm)

As far as the rest of the party, even without more sophisticated defenses up, attacking from the water is pointless because they can simply ready actions to whack it or sunder its tentacles.

[Karnith]

At level 19, Mage 1 should have either a contingency, Freedom of Movement or Heart of Water up at all times. And that's if he's even really there. (http://www.d20srd.org/srd/spells/astralProjection.htm)
Or even just have Foresight (http://www.d20srd.org/srd/spells/foresight.htm) up so he doesn't get surprised.

[Eurus]

At level 19, Mage 1 should have either a contingency, Freedom of Movement or Heart of Water up at all times. And that's if he's even really there. (http://www.d20srd.org/srd/spells/astralProjection.htm)

As far as the rest of the party, even without more sophisticated defenses up, attacking from the water is pointless because they can simply ready actions to whack it or sunder its tentacles.

At level 19, a single cr 19 monster is a speed bump, heh.

That's not to say that the octopus would be much of a threat to a level17 party either, granted. Very few things outside of monsters with full spellcasting are.

The poor octopus has zero ranged options, so it's not going to do much even at mid levels. The only real advantage it has is its environment, which does help, but even if you're fighting it underwater for whatever reason it's still vulnerable byn nature of being a big melee bruise r solo and overwhelmed by the action economy.

And that's the issue with CR, really. It's not just about numbers, or it shouldn't be. Mobility, range, defenses beyond just hp and ac. Number of actions is a big one, and more bodies means harder to pin down with single target disables. Things like incorporeality can be a massive factor. Spells, of course. Even intelligence. But those are things that the printed CR rarely accounts for. See, as an example, the tarrasque or hilarious destruction bugs.

[zlefin]

no, the CR system isn't completely borked.
It's not perfect; but the base numbers work reasonably; the CR adjustments for templates and extra HD may be a bit off, but they too tend to be a reasonable approximation.
They do note that when you stack a whole lot of stuff on the system gets a bit less accurate.
I don't see anything in the giant octopus entry about when it would advance to colossal; and the entry i'm looking at (srd) only goes up to huge, with no listing for gargantuan or colossal.

Also, you made some mistakes in your upgrading of the monster; which will cause some inaccuracies, specifically yours is rather weaker than it would actually be.

If you want, I can figure out what the monster stats should be.

[Zancloufer]

So I will admit to not completely understanding the CR system, but it's something I have trouble with gauging on occasions. I mean I've seen CR ~20 encounters stomped by the party I DM, but the same party had trouble facing off a CR ~10 encounter (I kid you not).

Okay, I went and did a full stating of my 26 HD, CR 19 Collassal Fiendish Octopus and here is what I got:

Size/Type: Colossal Animal (Aquatic)
Hit Dice: 26d8+211 (341 hp)
Initiative: +1
Speed: 20 ft. (4 squares), swim 30 ft.
Armor Class: 22 (-8 size, +1 Dex, +19 natural), touch 3, flat-footed 21
Base Attack/Grapple: +24/+58
Attack: Tentacle +34 melee (1d4+15)
Full Attack: 8 tentacles +34 melee (1d4+15) and bite +34 melee (1d8+22)
Space/Reach: 30 ft./30 ft. (40 ft. with tentacle)
Special Attacks: Improved grab, constrict, Smite Good
Special Qualities: Ink cloud, jet, Dark Vision, DR 10/Magic, DR 10 Fire and Cold, SR 31
Saves: Fort +24, Ref +17, Will +11
Abilities: Str 46, Dex 13, Con 27, Int 3, Wis 12, Cha 3
Skills: Escape Artist +11, Hide +3, Listen +8, Spot +10, Swim +41
Feats: Alertness, Skill Focus (Hide), Toughness + 6 others
Environment: Warm aquatic
Organization: Solitary
Challenge Rating: 19
Advancement: -
Level Adjustment:

Now a few things I DID miss included the massive STR/Grapple bonuses and the fact that being Fiendish makes it a Magical Beast instead of an animal.
Now as for the Size increase, iirc it DOESN'T say you can't make it bigger, it's just that I interpreted the advancement rules as points where it WOULD get bigger. So I put on 2 extra HD when I advanced it two sizes.

Now it's strengths seem to be 40ft reach and +58 Grapple. Not to mention SR 31 is somewhat effective at CR 19. However, this is a one trick Octopus. His 3 touch AC means he can't dodge crap, and the 22 base AC is little more than a "No you Can't dump all 19 BAB to power attack his face off". I mean playing him from a suddenly deep pool of water and jumping the party with up to 8 grapples seems to be about his only trick.

So the question is: What would make him worth of a CR 19? Also what CR COULD he be? His grapple and SR are insane enough that at a lower CR he would really pack some pain, but surprise with his +3 to hide seems to be his only hope of not dying horribly here.

[zlefin]

I've got a game starting right now; but I'll be done with that in an hour or so and I'll review, double check the stats, and add comments.
Also, fiendish is a rather weak template; and the +2cr from it is excessive; half-fiend on the other hand, can be a quite powerful template; and would make this thing scary powerful.

[Flickerdart]

Generally, advancing by many HD isn't a good plan for making monsters viable. If you have to add more than 8 or so, it's likely that the monster won't perform well anyway.

[Yawgmoth]

Everyone saying the CR system isn't completely borked has never run a D&D game before, or has run for players who choose each feat and class level at random. Because honestly there's just too many things I can point to and say "this will die at the hands of whichever PC rolls the highest initiative" and roughly as many "this will absolutely destroy a party at that level unless they specifically prepare for the fight and even then it depends on the dice."

The only thing CR is good for is as a collating value for a database, and even then it sucks because I still have to set my parameters +/-4 to get something that might be an agreeable difficulty, which is not a guarantee.

[Zancloufer]

Generally, advancing by many HD isn't a good plan for making monsters viable. If you have to add more than 8 or so, it's likely that the monster won't perform well anyway.

I Don't know, Outsiders and Dragon's aren't to bad for advancing HD. Especially since every 2 Dragon HD not only equals +1 CR, but +1 CL for them. Combined with having best everything, dragon Racial HD might be one of the most powerful bonuses you can give monsters relative to CR enhancement. For my poor octopus here, yeah I can see that.


Everyone saying the CR system isn't completely borked has never run a D&D game before, or has run for players who choose each feat and class level at random. Because honestly there's just too many things I can point to and say "this will die at the hands of whichever PC rolls the highest initiative" and roughly as many "this will absolutely destroy a party at that level unless they specifically prepare for the fight and even then it depends on the dice."

The only thing CR is good for is as a collating value for a database, and even then it sucks because I still have to set my parameters +/-4 to get something that might be an agreeable difficulty, which is not a guarantee.

Reminds me of my example earlier. Looked at the monsters I made more closely, my 6 Advanced CR 10 Maticores are equal to ~CR 15, but two CR ~19 Night Crawlers where about CR 21. Guess which one my party stomped, and which one almost killed the party twice over?

[AMFV]

It's a good baseline, better to know your groups strengths and weakness. If they aren't good at putting out damage then they will do poorly against large bag of HP monsters regardless of CR. If they aren't good at crowd control, they won't do well against groups or flying monsters. If they don't have defenses and contingencies they won't do well against offensive powerhouses. Just modify the CR as necessary for your own group's strengths and weaknesses otherwise it is a good baseline.

[Flickerdart]

I Don't know, Outsiders and Dragon's aren't to bad for advancing HD. Especially since every 2 Dragon HD not only equals +1 CR, but +1 CL for them. Combined with having best everything, dragon Racial HD might be one of the most powerful bonuses you can give monsters relative to CR enhancement. For my poor octopus here, yeah I can see that.

Dragons are practically a class - advancing them by HD also advances them by age category, which gives them a ton of goodies. Non-true dragons usually have abilities that scale with HD (breath weapon) and/or flight, so they do alright.

[Lord Vukodlak]

Your still missing some stuff Zancloufer, when a creature goes up in size its natural weapons increase by a die step.

So its tentacles should deal 2d6+18(you also had the strength calculated in correctly). If you gave it the feat Improved Natural Attack Tentacle, they'd deal 3d6+18.

[Grollub]

I think one thing people overlook on the CR system.. that , I believe, it's based on the average party.. if your group is optimizers, specialized, or gimps.. there will be a fight imbalance.

[Kyberwulf]

I seem to recall challenge ratings set to a particular set of classes.(A Fighter, A Cleric, A Rogue, and A Wizard) Also set to a specific WBL.
So if you mess with either of those, the CR of a monster will change accordingly.

In most cases, CR goes out the window as soon as you start playing. For a monster, or a group of monsters to be effective. You need to know your players.

[Ramza00]

The monster in your example has no special attack so more HD just means more Bab, hit points, and higher saves

Give them an offensive ability which has a DC that scales by hit dice and suddenly that monster is a lot better.

[Winds of Nagual]

What boggles my mind is the CR of NPCs!! So a lvl 5 fighter should be a normal challenge for a party of lvl 4 PCs? Unless amazing preparations are in order - they will mop the floor with the poor guy.

[Emperor Tippy]

It's decent for groups relatively new to the game and/or relatively low op.

It remains decent for experienced groups at mid (and even on occasion high) op if the DM actually plays the monsters to their ability scores and abilities.

Take, for example, a Pit Fiend. It has at Will Greater Teleport, at will invisibility, at will fireball, a fly speed, and Int and Wis scores of 26.

If you put a Pit Fiend within melee range of an ECL 20 party then the Pit Fiend will die in a round or so.

Now have that same Pit Fiend engage by dropping a Fireball onto the party from 1,100 feet away before Greater Teleporting to somewhere else within range and dropping yet another Fireball. Played smart (and with it's Int score it should be played very smart), a core only ECL 20 party is going to have a very difficult time actually fighting said Pit Fiend.

Outside of core it becomes easier but the Pit Fiend also gets access to non core abilities. Like a Persistent Fiendish Quickening, which gives it at will quickened greater teleport and Supernatural Transformation, which strips the SR off of Fireball.

A level 20 party that knows what it is doing (or even a single level 20 PC) could deal with such a Pit Fiend relatively easily. Have the party wizard Shapechange to Spellweaver form as a free action and use Mindsight along with your thousand mile telepathy to locate the Pit Fiend before greater teleporting the party near the Pit Fiend and using Celerity to cast Time Stop before activating a Weirdstone (or casting Dimensional Lock or another anti-teleport measure) and throwing up a Widened Mastery of Shaping Force Cage to contain the Pit Fiend with the part's melee brusiers).

On Melee's turn one of them triggers a Selective Antimagic field contingency and wades in to pound the Pit Fiend to dust.

Total resource expenditure was about in line with what should be expected for an equal CR challenge, risk was relatively minimal.

----
The big reason people bitch about the CR system is that they are unwilling to optimize either the monsters or the PC's as their stats and situations dictate. 18 Int is "super genius", 26 Int is "quite a bit smarter than the smartest human who has ever lived", 40 Int is "I can re-derive modern chemistry and win Nobel prizes in the field after having sat through a single semester of a highschool into to chemistry class."

Now how do you think something that smart (and often with a thousand plus years of life experience and massive magical power) is going to conduct a life or death fight?

[zlefin]

So I will admit to not completely understanding the CR system, but it's something I have trouble with gauging on occasions. I mean I've seen CR ~20 encounters stomped by the party I DM, but the same party had trouble facing off a CR ~10 encounter (I kid you not).

Okay, I went and did a full stating of my 26 HD, CR 19 Collassal Fiendish Octopus and here is what I got:

Size/Type: Colossal Animal (Aquatic)
Hit Dice: 26d8+211 (341 hp)
Initiative: +1
Speed: 20 ft. (4 squares), swim 30 ft.
Armor Class: 22 (-8 size, +1 Dex, +19 natural), touch 3, flat-footed 21
Base Attack/Grapple: +24/+58
Attack: Tentacle +34 melee (1d4+15)
Full Attack: 8 tentacles +34 melee (1d4+15) and bite +34 melee (1d8+22)
Space/Reach: 30 ft./30 ft. (40 ft. with tentacle)
Special Attacks: Improved grab, constrict, Smite Good
Special Qualities: Ink cloud, jet, Dark Vision, DR 10/Magic, DR 10 Fire and Cold, SR 31
Saves: Fort +24, Ref +17, Will +11
Abilities: Str 46, Dex 13, Con 27, Int 3, Wis 12, Cha 3
Skills: Escape Artist +11, Hide +3, Listen +8, Spot +10, Swim +41
Feats: Alertness, Skill Focus (Hide), Toughness + 6 others
Environment: Warm aquatic
Organization: Solitary
Challenge Rating: 19
Advancement: -
Level Adjustment:

Now a few things I DID miss included the massive STR/Grapple bonuses and the fact that being Fiendish makes it a Magical Beast instead of an animal.
Now as for the Size increase, iirc it DOESN'T say you can't make it bigger, it's just that I interpreted the advancement rules as points where it WOULD get bigger. So I put on 2 extra HD when I advanced it two sizes.

Now it's strengths seem to be 40ft reach and +58 Grapple. Not to mention SR 31 is somewhat effective at CR 19. However, this is a one trick Octopus. His 3 touch AC means he can't dodge crap, and the 22 base AC is little more than a "No you Can't dump all 19 BAB to power attack his face off". I mean playing him from a suddenly deep pool of water and jumping the party with up to 8 grapples seems to be about his only trick.

So the question is: What would make him worth of a CR 19? Also what CR COULD he be? His grapple and SR are insane enough that at a lower CR he would really pack some pain, but surprise with his +3 to hide seems to be his only hope of not dying horribly here.


ok, reviewing stats.
as to BaB; my guess would be that first you advance the HD, and then do the template; as the template says you shouldn't adjust the base creatures BaB due to the type change; you seemed to apply the template first; then add the HD, so the added HD used the BaB from the new type. I'm not sure which is correct, or if it's just plain unclear by RAW. My way would lower BaB by 5.

You're using the wrong STR mod, for a number of things; with 46 strength, it should be +18. The size increase also increases the natural attack dice size. So that would get the damage to 2d6+18 per tentacle.
As to their range; while not specified in the entry, I don't think it's +10' but rather twice standard reach; as per normal for reach weapons. So that'd be a 60' range on the tentacles.

Optimization levels will have some effect.

He gains I reckon, 18 skill points for his extra HD. Where you put those would have some effect on his power. Putting them all in Hide might make sense, as he really doesn't need escape artist as he gets bigger, and doesn't need swim much either. So full hide, or a mix of hide/spot/listen. Skills are always a bit odd on creatures though.

Now to figure out feats; also, as he passed 20 HD, he's eligible for epic feats for his higher end feats.
I'll recommend some feats that would likely be used by typical monsters; and hence the optimization level will only be moderate-low.

Improved Natural Attack (tentacle) this up them to 3d6. I'm not sure how constrict damage increases from levels up and strength; that's really quite vague in the rules; but it probably increases somewhat.

Improved Initiative.
Iron Will (in higher op games, steadfast determination)
Stealthy

this is sticking to stuff on the SRD; using other books would add some nice options to this.

For the 2 epic feats, i'd recommend some of these:
Unholy Strike (will let all the attacks count as having the Unholy weapon mod).

Epic skill focus (hide) if you put enough ranks in hide to be eligible, this can get you up to a +30-ish hide check.

Dire Charge - because full attacks are awesome.


He'd be an ambush predator; hiding, or moving around while staying well below the surface, if facing dangerous opponents would prefer murky water; and open up with a powerful attack. Anything which somehow doesn't have freedom of movement at that level would likely get grappled (which means constrict damage). Also note that while improved grab is a sweet ability; having to hit their regular ac for the tentacle attack first may be hard, so some tentacles will just go straight to grapple. If something charges it; it should use the attack of opportunity to grapple, which would stop the movement.

Fiendish is a template which charges a bit too much CR for its' limited benefits; it's more like a cr+1 at best.

If you want something more dangerous, use a scarier template like half-fiend; if party is high optimization, then improve the optimization of the feat selection and tactics of the monster (I can help with that if you want and can list sourcebooks eligible to use).

I couldn't find much about things that would increase swim speed.

[erikun]

Two things to note about the CR system.

First, optimization varies over the CR scale. MM1 creatures are typically very low-op, while later MM creatures tend to be noticably higher-op.

Second, CR equal to the party is intended to be a simple fight that then generates XP. CR 19 is in no way really intended to take out a four-person 19th level party. CR+4, or CR against a single opponent, is intended to be a challenge. This may not matter against a prepared Wizard (who isn't really challenged by anything at this point) but against a lone 19th level fighter, or against a relatively mid-op 15th level party, your octopus might come off as a threat.

[Big Fau]

The monsters of 3.5 suffer from two real problems:


The monster is little more than a bag of numbers, which stops being a credible threat sometime around 7th level.
The monster's abilities are heavily limited by the action economy.


The octopus in your OP? It suffers from both, and wouldn't really be an appropriate challenge past 7th or 9th level. This is usually the case with templated enemies and enemies advanced a couple HD.

Monsters that defy those two problems are either capable of casting spells from the Cleric/Wizard/Druid list or were designed late in 3.5's lifespan (MM4 or MM5 being decent examples).

[Zancloufer]

Odd that I missed Dice damage size. I also know it need 6 more feats, I just didn't think of any at the time. I don't seem them making a huge differeance though, mostly just numbers on a creature that's only good for numbers.

So it seems my Oversized Fiendish Octopus suffers from a variety of things that make it not overly CR appropriate. Size and HD advancement don't seem to mean much on their own without something else keyed of them? Also I think that Magical Beasts and Animals seem to get the short end of the stick especially with HD advancement.

Now two more small questions about the CR system while we are on the subject:

1) CR increases by +1 or +2 for having a "Minor" or "Major" special ability that improves said creature. What abilities would count as that? What could be tacked onto a large dump creature that would increase it's actual power relative to it's CR?

2) Making monsters from scratch. Using racial HD and Stat arrays I somewhat understand, but how would to CR that from the beginning?

[Urpriest]

You can't even legally make this thing. Giant Octopus advancement stops at 24HD Huge. It's an Animal, so it gets +1 CR/3HD (and the same is true if you advance it as a Magical Beast). It's already Large, so increasing in size won't increase its CR. So CR 8+5 for the 16 HD+2 for Fiendish=15. I don't get where you're getting CR 19 from.

Now granted, that's still pretty wimpy for a CR 15, but so is a 15th level Tordek.

[Zancloufer]

You can't even legally make this thing. Giant Octopus advancement stops at 24HD Huge. It's an Animal, so it gets +1 CR/3HD (and the same is true if you advance it as a Magical Beast). It's already Large, so increasing in size won't increase its CR. So CR 8+5 for the 16 HD+2 for Fiendish=15. I don't get where you're getting CR 19 from.

Now granted, that's still pretty wimpy for a CR 15, but so is a 15th level Tordek.

Is there any RAW against advancing it past 24 HD? As far as I can tell there isn't but I'm not certain which is why I'm asking.

Also doesn't going from Large to Huge give it +1 CR? If we remove 2 of it's HD and two size advances it drops to 16 CR. Or does the advancement rules mean it gets that size increase for free with HD advancement?

EDIT: I would also like to give you props for your monster guide it did help explaining just about everything about monsters, except the CR system

[Eldariel]

CR system is by definition broken since it assumes uniform class power for all characters of the same level. Even without delving into theoretical optimization, a Wizard 5/Incantatrix 10 is probably slightly more terrifying (as in, capable of doing everything the other is, then some, and boning reality in the backside while at it) than even the most optimized Monk 15, let alone a hodgepodge of classes that does nothing.

However, CR assumes their performance is very close to each other, or identical, while Incantatrix is borderline-unkillable, can actually outdamage the Monk with a single spell, can recharge his spells for effective unlimited spells per day, etc. Basically, even just numerically we're talking about comparing someone with ~hundred HP to someone who cannot die to due to damage. Then there's a spectrum there with tons of different levels of performance at each level.


Then there's CR based on levels. Non-associate class levels are kinda ridiculous, advanced HD doesn't work most of the time (try advancing a Gibbering Mouther for instance, and compare the advanced Mouther to any creatures of equal CR), creatures with stupid CR to start with (why, Disjunction is totally something level 9 character should be able to deal with, right Adamantine Clockwork Horror?), etc. Basically, the system is useless. Rather eyeball, use leveled creatures of your own creation and enemies that make sense for the region. An experienced GM can rate the difficulty of any creature they're using without so much as glancing their CR, and much more accurately than the CR (and he knows the power of the party with respect to their level).

[3WhiteFox3]

CR system is by definition broken since it assumes uniform class power for all characters of the same level. Even without delving into theoretical optimization, a Wizard 5/Incantatrix 10 is probably slightly more terrifying (as in, capable of doing everything the other is, then some, and boning reality in the backside while at it) than even the most optimized Monk 15, let alone a hodgepodge of classes that does nothing.

However, CR assumes their performance is very close to each other, or identical, while Incantatrix is borderline-unkillable, can actually outdamage the Monk with a single spell, can recharge his spells for effective unlimited spells per day, etc. Basically, even just numerically we're talking about comparing someone with ~hundred HP to someone who cannot die to due to damage. Then there's a spectrum there with tons of different levels of performance at each level.


Then there's CR based on levels. Non-associate class levels are kinda ridiculous, advanced HD doesn't work most of the time (try advancing a Gibbering Mouther for instance, and compare the advanced Mouther to any creatures of equal CR), creatures with stupid CR to start with (why, Disjunction is totally something level 9 character should be able to deal with, right Adamantine Clockwork Horror?), etc. Basically, the system is useless. Rather eyeball, use leveled creatures of your own creation and enemies that make sense for the region. An experienced GM can rate the difficulty of any creature they're using without so much as glancing their CR, and much more accurately than the CR (and he knows the power of the party with respect to their level).

Other problems:

Monster challenge can vary wildly in the same group depending on when the group fights a monster. Compare a Vampire Human Warrior 5 at CR 4 against a standard 1st level party and the same monster with 16 Warrior Levels at CR 10 vs a standard 7th level party. At first level, the characters are almost certainly going to TPK at all but the highest levels of optimization, at 7th level, they stand a much better chance and the fight is merely going to be very difficult as intended (or less difficult depending on character loadout). This doesn't take into count all of the various Vampire weaknesses and whether or nor Characters can exploit them. However, at level 7 with 4th level spells and better equipment, the party has better chances to take advantage of those weaknesses. Templates as a whole cause this problem, throw a template on a low CR monster and throw it against a low-level party, chances are that even with equal CR, the monster will pose a significantly higher challenge.

Another issue is that most monsters are hard if you are unprepared or don't know their trick but easy if you do. Werewolves, Rust Monsters, Golems and their magic immunity, incorporeal creatures, low-to-medium optimized spellcasters; all of these can range from trivially easy to very difficult depending on how well the party knows the game. This is because many tactics have direct counters, bring silver against the Werewolf, use spells and non-metallic weapons against the Rust Monster, have SR: No spells against the golem, etc...

Now, the designers realized this somewhat, giving examples of how some monsters might be more dangerous when given advantages, but it doesn't help groups that expect the CR system to work as a strong guideline for encounter difficulty nor does it work for those groups that primarily run modules, since I have never seen the monsters in a module to be given higher CRs dependent on party composition (or even a sidebar explaining that it might be more difficult against certain groups), or on the advantages given to certain monsters.

[Urpriest]

Is there any RAW against advancing it past 24 HD? As far as I can tell there isn't but I'm not certain which is why I'm asking.

Also doesn't going from Large to Huge give it +1 CR? If we remove 2 of it's HD and two size advances it drops to 16 CR. Or does the advancement rules mean it gets that size increase for free with HD advancement?

EDIT: I would also like to give you props for your monster guide it did help explaining just about everything about monsters, except the CR system

There isn't any way to advance it past 24 HD. You don't know what size it would become, for one (and it certainly wouldn't be Colossal).

It's not that you get the size increase "for free" with HD advancement, it's that according to the table you only get the +1 CR when you first increase to Large or larger (via HD advancement, note. You can't just add size categories willy-nilly, there aren't any provisions for that). If you're already Large, there's no increase.

The thing about the CR system, it's mostly about making sure that the numbers match up, and determining XP. As long as attack bonus and hp scale at about the right rates, that's all the CR system is designed to do. Actual difficulty isn't what it measures. Sometimes you'll have an easy fight that grants a lot of XP because it has high EL, or a hard fight that doesn't grant much XP because it's low EL.

[zlefin]

there's no RAW specifically supporting it; but I see nothing specifically prohibiting a DM from pushing monsters to even higher HD totals and increasing size as desired. It's just not a specifically supported plan.

Just because there's a number of issues doesn't mean it's completely useless; just imperfect and inaccurate; especially if you learn a bit about which parts to adjust for.