[3.5] Monster Advancement Advice Needed

[Thurbane]

I have a question about advancing monsters with templates.

I've asked this in the Q&A before, but I don't think I got a clear answer.

Say I have a Monstrous Humanoid (which normally increases by +1 CR for each 3 HD advanced); I then give it an inherited template which changes its type to Fey (which normally increase by +1 CR for each 4 HD advanced).

Which figure do I use for its advancement?

Technically, since it's an inherited template, my gut feeling is +1 CR for each 4 HD, since it's always been a Fey.

But then again, say the template doesn't affect BAB or saves - the creature advancing is then more in line with a Monstrous Humanoid with its advancement.

If I seem vague by not mentioning specifics of race or template, it's just in case any of my players are reading this.

Cheers - T

[A_S]

My intuition is that you should go with the CR/HD ratio of the base creature's type. That ratio is basically a measure of how "good" each HD is; since templates typically don't change the features of the base creature's hit dice (how many HP they grant, what BAB they come with, saves), the base creature is going to be a better estimate of how good each HD is than the new type.

I haven't found a solid citation for this, though.

[Urpriest]

The rules don't really specify. As you point out, it makes a bit more sense to go with the "original" type, as long as it's the one providing the features of the HD. One thing to remember is that HD advancement can be just as "inherited" as an inherited template: while sometimes HD advancement represents growth, it can also simply represent unusually powerful specimens.