Simple enough question.

Background:
The party I am DMing for, lost their (badly unoptimised) Cleric last night to a minor BBEG, who then escaped.
In his laboratory they find, amongst the tied up and tortured-almost-to-death 'test subjects', a Unicorn and a Centaur.
I can run with re-working the Centaur into a half-decent cleric, but I was just wondering if the Unicorn might just fit?

The party are CL13, the cleric (because of race shenanigans) was L9.