That's a pretty good write-up. However, since it only works the first time a creature sees it, there's no need for the 24 hour immunity line.And let's make "the save DC is Charisma-based" a separate sentence.
If it has an alien mind, then it shouldn't be mindless. Actually it shouldn't be mindless in the first place if it's an aberration. I should point out that the carrion crawler, which was non-intelligent in previous editions has an intelligence of 1.
I'm fine with Cleon's writeup, including allowing it to happen more than once.
Here's another ability that might be fun to modify:
Alien Mind (Su): While a minion of chaos is not immune to mental attacks, anyone targeting it with a mind-affecting or telepathic effect makes direct contact with its utterly alien mind. The attacker must make a DC 34 Will save or take 1d4+1 points of Wisdom damage. An attacker is subject to Wisdom damage on every attempt, whether the attack is successful or not. The save DC is Charisma-based.
I like all that.
Immolation seems pretty straight-forward, though I have two questions. Should it do fire damage or half-fire/half-untyped damage? And does it just do 6d8 damage once, or should it keep burning over a few rounds (with maybe a chance to put it out)?