When you hold forth a bit of one beast (fur, bone, etc.) and speak the words of chimeric transmogrification upon another, roll +INT: on a 10+, the spell works; on a 7-9, the spell works but only if you mark a debility.

When the spell works, roll 1d10+CON. If your roll equals or exceeds the target's current HP, name a feature of the beast you hold—the target's form twists and buckles, gaining that feature until they sleep for a few hours. The experience is disorienting and alarming; most beasts and people will panic. If you roll less than the target's current HP, their form twists and buckles alarmingly for a few seconds, but they fight off the transformation. Either way, the bit of the beast you hold is lost, shriveling away to nothing.