Number of allies is tied to difficulty: 

Easiest: 4 fledgling vampires, 2 grimwards
Easy: 2 fledgling vampires, 2 vampires, 2 grimwards
Core: 4 vampires, 2 grimwards
Hard: 2 vampires, 2 vampire mages, 4 grimwards
Insane: 2 old vampires, 2 vampire mages, 6 grimwards

as are Bodhi's spell-like abilities:

Easy: Buried Alive, Touch of Death, Call of the Mistress
Core: also Cloud of Bats, Abyssal Darkness, Sepulchral Sleep
Hard: also Chill of the Grave
Insane: also Deathly Shroud

On Insane, Bodhi also gets +1 attack per round and is immune to L1 and L2 spells, and gets a second wind at 10% hit points


