Obzedat, Ghost Council

When Obzedat, Ghost Council enters, target opponent loses 2 life and you gain 2 life.
At the beginning of your end step, you may exile Obzedat. If you do, return it to the battlefield under its owner's control at the beginning of your next upkeep. It gains haste.

Explorer Anthology 3

Modern Masters 2017

When Obzedat, Ghost Council enters the battlefield, target opponent loses 2 life and you gain 2 life.
At the beginning of your end step, you may exile Obzedat. If you do, return it to the battlefield under its owner's control at the beginning of your next upkeep. It gains haste.

Gatecrash

If you gain control of Obzedat “until end of turn,” you’ll control it during your end step and you choose whether to exile it. If you do, it returns to the battlefield under its owner’s control at the beginning of your next upkeep, not its owner’s next upkeep.

Once Obzedat’s ability has returned it to the battlefield, it has haste for as long as it remains on the battlefield. If an opponent gains control of it (perhaps with Olivia Voldaren or Soul Ransom), it can attack that turn.