[Taqwus]

Astral may or may not be dangerous; depends on whether or not your pretender will ever fight.
A warm-blooded pretender with C'tis Miasma, or a living pretender with Ashen Empire / Soul Gate may be a bad mix.
Sending a pretender into the arena is generally not recommended -- too easy to boobytrap (e.g. curse, lycantropos amulet, decay, disease, a pair of eyes, etc).