Rise of the Skull Servants

Create a X/X+1 black Skeleton Noble creature token with decayed, where X is equal to the number of cards you own in exile and in your graveyard that are skeletons or named Rise of the Skull Servants.

Whenever a skeleton you control is sacrificed, you
may cast this spell from your graveyard. If you do, exile it.

A deck can have any number of cards named
Rise of the Skull Servants.