Calculating CR of Glass Cannons (3.5)

[Fiery Diamond]

So, my question really boils down to this: Say I homebrew a monster. If its hit points are low compared to its combat/magic ability, how should I handle calculating CR?

For example:
A creature with low HD but insanely good chance to deal high amounts of physical damage.
A creature with low HD but insanely good chance to deal high amounts of magical damage.
A creature with low HD but capable of inflicting almost any status effect in the game multiple times a round to creatures in melee reach.
A creature with low HD but capable of avoiding damage and negative status effects most of the time and capable of dealing massive amounts of damage (physical and magical).

And similar things.

[term1nally s1ck]

Just base it on how much damage it does. CR-appropriate should take 1/4 of the party's resources(HP, spells/day) to kill, so it needs to do a lot of damage if it's going to die straight away. Basically, pretend you have 4 of them, and if that's an even fight (equal chances of victory), it's the same CR as the party's level.

[Eldariel]

The game already has those; Beholders are pretty much ur-example of "I have a thousand tons of pain to dish out, but touch me and I die" and Hydras are quite far up there too. So...the same. Expect the battles to be more tactical than standard as the party is well-advised to either try to kill it before it can act, or try to negate its actions even expending multiple party member's actions while dropping it, but don't artificially inflate its CR (just remember that such creatures can be useful for challenging higher-level characters too since while they go down fast, their offense tends to be sufficient that they're still a serious threat making them optimal for using en masse later on for challenging, but not unwinnable fights); methods to accomplish just that do generally exist especially beyond level 7.

So...yeah, CR them like you'd CR anything else; put them at their offense and then drop them few CRs for not lasting as long as true CR X creatures should. Or use the book guidelines that should burn in the abyss.

[Xenogears]

Just base it on how much damage it does. CR-appropriate should take 1/4 of the party's resources(HP, spells/day) to kill, so it needs to do a lot of damage if it's going to die straight away. Basically, pretend you have 4 of them, and if that's an even fight (equal chances of victory), it's the same CR as the party's level.

But what if you make it High CR and it gets one-shotted? I think you should give it a CR after the fight to reflect how tough it actually was...

[term1nally s1ck]

If you have to do that, you can...but it's unfair, as then you wouldn't give xp to a party for taking down anything if they did it by luck.

If you're homebrewing a glass cannon, give it HIGH initiative. It wants to go first and get off the alpha strike before anything else happens.

[Xenogears]

If you have to do that, you can...but it's unfair, as then you wouldn't give xp to a party for taking down anything if they did it by luck.

It also means that bad luck that makes a party struggle gives more XP. Kinda enforces the idea that you learn more from hardship than ease. I mean one shotting a dragon, while impressive, doesn't teach you anything. Struggling for a few minutes against a pair of goblins you were sure you could take is more likely to.

[Thrawn183]

The creatures with the best offense are always easy to take down for their CR, see beholders and mind flayers.

[term1nally s1ck]

While that's true, and it would make sense in terms of giving XP, it's not much use for deciding what level monsters are appropriate for.

[drengnikrafe]

I was under the impression that CR is for new DMs who don't know how things interact yet, and by the time you're ready to start homebrewing things (rather then just tacking on a new name and appearence to an existing creature), you should know it well enough to not use it.