Dustwaker

When Dustwaker enters the battlefield, put a
Dust counter on target creature.
{t}: Put a Dust counter on target creature
Dustwaker's power and toughness is equal to the number of creatures with Dust counters on them.
Whenever Dustwaker deals combat damage to a
player or planeswalker, put up to one creature
with a Dust counter on it on the top of its
owner's library.