When Fiend Hunter enters the battlefield, you may exile another target creature.
When Fiend Hunter leaves the battlefield, return the exiled card to the battlefield under its owner's control.
Kicker (You may pay an additional as you cast this spell.)
When Gatekeeper of Malakir enters the battlefield, if it was kicked, target player sacrifices a creature.
Trample, haste
At the beginning of the end step, sacrifice Hellspark Elemental.
Unearth (: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)
When Mesmeric Fiend enters the battlefield, target opponent reveals their hand and you choose a nonland card from it. Exile that card.
When Mesmeric Fiend leaves the battlefield, return the exiled card to its owner's hand.