Bone Harvester

Bone Harvester cannot be sacrificed.
{t}, Exile 50 skeletons you control: Gain 50 life.
Whenever creature dies, put bone counter on a creature without a bone counter at random from creatures you control and don't control, that isn't a token skeleton creature.
Whenever a creature with a bone counter on it dies, create a nonlegendary 1/1 black skeleton creature token copy of it with "This creature
can't be sacrificed".