Birthing Ritual

At the beginning of your end step, if you control a creature, look at the top seven cards of your library. Then you may sacrifice a creature. If you do, you may put a creature card with mana value X or less from among those cards onto the battlefield, where X is 1 plus the sacrificed creature's mana value. Put the rest on the bottom of your library in a random order.

Sek'Kuar, Deathkeeper

Whenever another nontoken creature you control dies, create a 3/1 black and red Graveborn creature token with haste.