It's the same as when you use the upgrade stones. Over 21(?), the pet loses 2 levels, over 15(?), they lose 1 level, and the rest stay the same.
Dread Lörd Kaolian wrote:
As a forum admin, you... see things. Things that you can never unsee. Things that make you fervently wish to protect other people from ever seeing those things. This is why forum admins are sometimes cranky.