The other way around, I’d say.

then we could put a little note afterwards such as [feats in brackets are alternates from the Book of Vile Darkness]
Ok, more stuff…
As for his bite attack, I’m thinking that it can only be used while grappling a creature, or instead of his normal attacks. His full attack routine should be “2 tentacles … and 2 arms … or bite”.
His Improved Grab line should read as follows:
Improved Grab (Ex): To use this ability, Kerzit must hit with both tentacles. It can then attempt to start a grapple as a free action without provoking an attack of opportunity. If it wins the grapple check, it establishes a hold and automatically deals bite damage.
How would we write up his smell immunity? Just “Kerzit is immune to all spells of 3rd level and lower”? such as minor globe of invulnerability, like Clifford suggested.
What, therefore, should his SR be? It need not be particularly high, since he does have that nice little immunity.
I noticed that we have a listing for see invisibility in the special qualities, and he also has that as a spell-like. should I keep it as a spell-like, or copy the see invisibility (Su) power of demons?
And… posting Kerzit in homebrews, so check him out.
