The Cauldron of Eternity 
Legendary Artifact
This spell costs 
less to cast for each creature card in your graveyard.
Whenever a creature you control dies, put it on the bottom of its owner's library.
, 
, Pay 2 life: Return target creature card from your graveyard to the battlefield. Activate only as a sorcery.
Legality
standardNOT LEGALpioneerLEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL