Aven Augur

The sacrifice clause is doing the heavy lifting here, and the upkeep restriction is what keeps the bounce from being a free instant-speed blowout. Tempo flyers that bounce things on their way out are common; the wrinkle is the timing window. You cannot hold this Bird up as combat-trick insurance or fire it in response to a removal spell mid-combat. It only fires during your own upkeep, before you draw, before you act: a deliberately telegraphed reset rather than a reactive answer. That turns a creature most decks would treat as a body with an emergency button into something closer to a slow-burn engine, one that asks you to want the bounce on a schedule rather than at the moment of crisis. Returning up to two creatures means it scales from a one-target tempo swing to a two-for-one against a developed board, and "their owners' hands" lets it reset your own enters-the-battlefield triggers as readily as it strands an opponent's. The whole shape rewards a deck built to know, a turn in advance, what it wants to pick up and replay. The design reads as undertuned until you sit with the constraint and recognize that the upkeep lock is precisely what stops the effect from being oppressive, and precisely what makes it a planned maneuver rather than a panic button.