Xahna, Earthen Nightmare

Delve
Rebirth (when this creature enters the battlefield, return target creature from your graveyard to the battlefield attached to this creature, at the beginning of your upkeep, cast the attached creature without paying its mana cost)
New Evolution (If you control Xahna, Earthen Nightmare, Anusara, Pathmaker, and Sauron, Guardian of Evil, exile them and meld them into Xanuran, Embodiment of Nightmares)