Destroy target permanent. Its controller creates a 3/3 green Beast creature token.
6/1/2011 If the permanent is an illegal target when Beast Within tries to resolve, the spell won’t resolve and none of its effects will happen. The permanent’s controller won’t get a Beast token.
7/1/2013 If the permanent is still a legal target but is not destroyed (perhaps because it regenerated or has indestructible), its controller still gets the Beast token.