Volrath, the Shapestealer
From Commander 2019 set
Volrath, the Shapestealer
Legendary Creature — Phyrexian Shapeshifter
7/5
At the beginning of combat on your turn, put a -1/-1 counter on up to one target creature.
: Until your next turn, Volrath becomes a copy of target creature with a counter on it, except it's 7/5 and it has this ability.