Arewei, the Risen Mist

Creatures you control enter with an additional X
+1/+1 counters on them, where X is the players in
the game.

Whenever a nontoken creature enters the
battlefield under your control, each player creates a
tapped 1/1 blue Elemental with "{t}, sacrifice this
creature: Place a +1/+1 counter on target creature.
Activate only as a sorcery."