Blood Ritualist

{b}, {t}, Sacrifice two creatures: Demonize target non-Demon creature. (It gains "Cumulative upkeep - Pay 1 life" and "When this creature dies, return it to the battlefield under target opponent's control. It becomes a Demon in addition to its other types.")
"We're not losing you. We're just passing you on to something greater." - Liliana Vess