Volrath, the Shapestealer

A Shapeshifter that supplies its own targets is a rare thing, and the elegance here is how the combat-step -1/-1 counter seeds exactly the kind of body the copy ability wants to wear. Drop a counter on any creature at the beginning of combat, then pay one mana to become it. The catch is what carries over: the copy keeps only the 7/5 base body and the activation itself, not the triggered counter-placing ability, so the seeding and the stealing are two separate motions that happen to feed each other. Once he is wearing another form, he stops generating fresh counters until he reverts. The copy clause reads any creature "with a counter on it," which is the real width of the design: the -1/-1 trigger guarantees a legal target every turn, but a +1/+1-loaded threat, a charge-counter artifact creature, anything wearing a counter becomes a body to borrow. That width has a hard edge, though. Copy effects duplicate only printed values, so becoming an animated planeswalker means becoming a non-creature permanent with no starting loyalty; since he never entered, state-based actions bury him instantly. Read the board for genuine creatures, and he grinds it down between thefts: the -1/-1 trigger doubles as small-creature removal and a clean answer to indestructible bodies, while always leaving at least one counter somewhere that could become his next disguise.