Voidmind hydra

[Vahktang]

Our heroes are about to go up against a voidmind (m3, pg 187) hydra (m pg 155)
Can you have cut off all the heads but one, void mind that one, and it controls the others?
Or, do each of the heads have to be void minded?
If you do void mind all the heads, to they each get a spray, do they each get a tentacle?

Finally, only a +1 to CR?
You get stat bonus, a once/day breath weapon, bonus to AC, immune to some spells, immune to ability drains, etc, Spell Resistance, Damage Reduction, a tentacle attack, and the makers get to use your body to do it's abilities.
And it's only a +1 to CR?
I'm going to make it like the half celestial/half fiend, et al, Hit Dice resistant.

What think you all?

 

[Psion]

Finally, only a +1 to CR?
You get stat bonus, a once/day breath weapon, bonus to AC, immune to some spells, immune to ability drains, etc, Spell Resistance, Damage Reduction, a tentacle attack, and the makers get to use your body to do it's abilities.
And it's only a +1 to CR?
I'm going to make it like the half celestial/half fiend, et al, Hit Dice resistant.

I've seen a few people post that it should be +3, but I don't know if that comes from an errata or anything. Seems reasonable, though.

 

[Runestar]

A cr increase of +2 suggests that a voidmind hydra will be roughly equivalent in power to 2 normal hydras. Is a voidmind hydra that tough?

 

[Vahktang]

A cr increase of +2 suggests that a voidmind hydra will be roughly equivalent in power to 2 normal hydras. Is a voidmind hydra that tough?

Good point.
With SR and no ability damage _and_ an independent tentacle attack, I think so.