When Swift Warkite enters the battlefield, you may put a creature card with converted mana cost 3 or less from your hand or graveyard onto the battlefield. That creature gains haste. Return it to your hand at the beginning of the next end step.
You can’t put creatures onto the battlefield face down this way.
The creature you put onto the battlefield will be returned to your hand only if it’s still on the battlefield as the delayed triggered ability resolves during the next end step. If it leaves the battlefield before then, it will remain wherever it is.
The delayed triggered ability that returns the creature to your hand will trigger even if Swift Warkite leaves the battlefield before the next end step.