Sturrmgol, Shepherds' Bane

Whenever Sturrmgol or another Troll creature
enters the battlefield, put a +1/+1 counter on it
and each opponent creates a 0/1 white Goat
creature token.
Whenever you attack a player with one or more
Troll creatures, that player must sacrifice a
creature. Whenever a Bird, Goat, or Ox creature
is sacrificed this way, put a +1/+1 counter on
target creature and you gain 2 life.