Throt the Unclean

Master Mutator-Creature cards in your hand have mutate, the mutate cost is equal to its mana value reduced by {1}

Whenever a creature you control mutates, you may sacrifice another creature. If you do, add a +1/+1 counter to the mutated creature for each time it has mutated

{4},{t}: Create a 4/4 Rat Ogre creature token with trample