What's the deal with Mind Flayer CR?

[Pleh]

Looking to make a pretty standard Mind Flayer boss battle for one of my games, but the rules for making characters with Mind Flayers is making my head spin a bit.

Thing that's bugging me is that their CR seems to be equated to their HD, but they have a Level Adjustment +7. ECL is RHD+LA+Class Levels

If CR is supposed to be a case that a PC of Level X should win fights about 50% of the time with encounters CR X, then comparing an NPC Illithid with a PC that's just a clone of the same character renders ECL 7 levels higher than the NPC of the exact same statistics.

By CR math, the PC that is nothing but a bog standard Illithid should be pretty overpowering to the NPC clone of himself, but since they have the same stats, it would theoretically come out to be 50% wins.

How am I supposed to read how difficult the Boss is supposed to be when there's such a disparity between what the CR seems to be versus what the ECL of the NPC seems to be?

And don't waste my time with nonsense about "NPCs don't have ECL," I don't care about any of the technobabble. How exactly is this supposed to work, however you want to phrase it? I need to be able to custom craft what levels this guy is going to have and the math on the CR just isn't adding up with their rules on making characters.

If CR is just "total of their hit dice from race and levels," that's easy enough, but it doesn't quite feel right.

Party is level 9 and is sufficiently optimized in their approach to the game that level-appropriate CR is a little too easy. Standard boss battle CR would be around 12, so I was thinking a CR 13 encounter wasn't going to be far out of place (I want them to feel the heat and possibly face deaths, partly because this villain will be recurring and it'll be nice to have the motive to squish his face in next time they meet).

[DarkSoul]

If you're making a boss battle, ignore Level Adjustment, and read up on associated/non-associated class levels to reach the CR you're looking for.

If you're making an NPC that will adventure with the group, or a PC, then take LA into consideration so they don't completely overpower the group.

[Goaty14]

Yea -- LA is only if a player wants to use the race/monster (remember: PCs show up in parties of 4! Bosses show up in parties of... 1?). Mind, this is WotC, and the LA-Reassignment (http://www.giantitp.com/forums/showsinglepost.php?p=22020529&postcount=331) thread rates it 5 lower at +2.

Instead, you should be using the associated/nonassociated class rules to make your boss.

[Zaq]

It's not technobabble, unfortunately. NPCs don't have ECL. They have CR, and when you're dealing with anything other than "standard" races, ECL and CR really aren't the same thing. Per the rules, they straight up aren't calculated the same way. This is partly because 3.5-era devs were really bad at articulating how encounters are supposed to be designed, and so CR is generally assigned based on the concept of a party of PCs against a solo monster, which gets all kinds of horribly skewed and really isn't sustainable long-term once the PCs figure out how action economy works. But whatever the rationale, CR and ECL aren't the same thing.

As you're discovering, of course, WotC was really sloppy with assigning LA, and I honestly think it was mostly intended as a soft-ban ("okay, I guess we'll let you play this monstrous race if it matters to you that much, but we're going to punish you by making it suck hardcore") rather than as an actual balancing factor. It's a known problem. As has been mentioned, there's been some efforts here (and I'm sure elsewhere) to address such things.

When actually trying to figure out how an encounter will challenge a group of actual PCs, it's far better to rely on judgment rather than on the printed CR rules. Which sucks, and that's one reason why I hate GMing 3.5.

[Telok]

Note that mind flayers are in a tricky spot for CR too. They have an AoE will save stun, 1-4 round autokill on stunned, high SR relative to CR, and standard action at-will plane shift. So they're pretty nasty...

Unless your party has the ability to resist/ignore the saves or one-round-kill the critter. Then the poor things are just nuisance monsters. They have a pretty strong glass cannon vibe going on.

[kinem]

Some reasons that the proper ECL and CR can differ:

- PCs are assumed to have gear corresponding to the standard wealth by level and higher than average ability scores, both of which are substantial power increases.

- Adding a few class levels to some monsters can substantially increase their power, especially when combined with magic gear. For example, it doesn't take much to boost a monster's AC (starting with already high natural armor) by a significant amount by giving it a level of sorcerer and letting it cast mage armor and shield and having a higher than average Dex bonus.

- A glass cannon monster is much more powerful in a party than it would be alone.

- A monster may have abilities that are on par with daily use abilities, but usable all day long. That doesn't matter much for CR since it's based on a single fight, but matters a lot for PCs who can expect to face many encounters per day.

[Arael666]

By CR math, the PC that is nothing but a bog standard Illithid should be pretty overpowering to the NPC clone of himself, but since they have the same stats, it would theoretically come out to be 50% wins.

CR takes into account a party of 4 PCs, thus the ECL of the solo Illithid PC should be divided by four when calculating apropriate challenges.

[Jack_Simth]

Challenge Rating (CR) is intended as a rating of how hard it is for a party of four to take them on in a fight. Hit Dice (HD) impact it, but there's no direct correlation between HD and CR. You use CR for things that you expect the party to fight.
Effective Character Level (ECL = Level Adjustment (LA) + Racial Hit Dice (RHD) + Class Levels (CL)) is intended as a rating of how useful the abilities are over the course of a campaign. You use ECL for party members (Player Characters (PCs), cohorts, followers, hirelings, et cetera)

They're measuring different things, and so give different numbers. Take two (imaginary) creatures that are identical, except for one ability:
One of them gets Invisibility once per day, the other at will.
For CR, the difference between once a day and at will is very minor - it'll rarely be used more than once on screen anyway (starting an ambush), so the two creatures will generally have pretty much the same CR.
For ECL, on the other hand, the difference is pretty significant: At will has MUCH more impact in PC hands - scouting all the time, spying on folks, starting every combat unseen... once a day will see a lot less play. So the two creatures will probably have different Level Adjustment as a result.

Mind you: Neither is what I would call an exact science, and WotC had a VERY STRONG tendency to overrate racial abilities (possibly a deliberate move to make 'normal' characters the better choice normally). But they're measuring different and largely unrelated things.

[Eldariel]

Better example would be 1/day vs. 10/day. At-will is a substantial advantage for monsters too since it means they can remain invisible all day. Thus they don't need to detect the PCs somehow first to go invisible and attempt an ambush (a tricky proposition at best, unless DM metagames and gives monsters OOC info). Meanwhile at-will guarantees allday invisibility and thus ambush lest the PCs have ways to detect them. Further, at-will enables shadowing and studying the PCs and attacking when they are split/engaged with another enemy/etc. with good knowledge of their powers while 1/day is rather limited in duration even with a victory in the detection round. In general, at-will of short duration powers is immensely powerful in the hands of PCs and NPCs alike: it's equivalent to having it persisted at the start of the encounter far as the action economy cost goes. And e.g. at-will Invis can keep multiple creatures constantly invisible.

[Fizban]

As the others have stated, you've just run into an example of why that line of thinking doesn't work as well in practice as it does in theory.


If you want consistent results you can't expect a level based formula to give them, because class levels are (only) as powerful as you make them. The best way to assign the CR for any modified monster is to just do it yourself. Take whatever you've been using, be they completely stock monsters or fully customized classed builds, and aim for your adjusted Mind Flayer to hit the same target as your other methods.

If you must do so by a formula, then what you're looking for is the Mind Flayer advancement entry, which says Advancement: By character class, and Advanced Monster Challenge Rating on page 293-4 of the Monster Manual. Which states that. . . "Assigning a Challenge Rating is a subjective judgement, not an exact science." The crux of the issue is that of associated or non-associated class levels: bruiser monsters that add fighter or other full BAB levels theoretically at +1 CR for each level of fighter, and monsters with innate casting add +1 CR for each level of the same class, but standard Mind Flayers don't actually jive well with any class. Non-associated class levels add +1 CR/2 levels, because they're still hit dice and features.

So if you're using Psionic Mind Flayers with extra Psion levels, you add +1 CR for each extra level-this includes the Elite Array and gear based on it's ECL, though gear based on CR would make more sense and is already roughly equivalent to triple standard treasure.

If you're using standard Mind Flayers, then you have to decide what classes would "increase a monster's existing strengths" for a Mind Flayer- presumably classes that rely on mental stats and don't get in the way of/synergize with their innate abilities. Hexblade or Paladin of Tyranny would likely count. The MM clearly counts Sorcerer based on the CR 17 given for a 9th level Mind Flayer Sorcerer.

[lord_khaine]

Yea -- LA is only if a player wants to use the race/monster (remember: PCs show up in parties of 4! Bosses show up in parties of... 1?). Mind, this is WotC, and the LA-Reassignment thread rates it 5 lower at +2.

Instead, you should be using the associated/nonassociated class rules to make your boss.

The LA assigningment thread is just a group of faceless people on the net though. I think the debate back and forth around how a given creature should be rated is more important than what it is rated.

[Gnaeus]

Clearly the listed CR of mind flayers is a result of racial animus by people with faces.

[Kayblis]

CR has nothing to do with ECL. They have different purposes.

Mind Flayers have a very high ECL for their at-will abilities and SR, so it's a CR 8 monster with a huge SR that's seen as merely "good" at level 15. At-will Charm Monster is very very OP, only getting less OP at higher levels because of the low-ish DC. The instakill is also very strong, goes off the same target list as Sneak Attack but is much harder to get immunity to.

I believe the high ECL is based around poorly optimized PCs. A Mind Flayer at level 15 in a common table is a consistent threat to non-immune targets, and most tables don't revolve around exclusively immune monsters(specially of they have a rogue). It is a very fragile character, though, can be downed in two to three hits by most relevant threats and everything it has other than Extract offers a roll, be it a save or a very-unlikely-to-hit Grapple check. I believe the +2 LA given by the local LA Assignment thread is better suited for higher optimization games, as the creature also has EIGHT RHD that don't contribute to the monster's abilities at all. A Mind Flayer at ECL 10 isn't behind the curve compared to most decent builds.