If I Akshan an opponent's gear, using Pack of Wonder to return my opponent's gear to my hand, play my opponent's gear, then kill off my Akshan, does my opponent's gear return to their field?

The Ruling

No, the gear does not return to the opponent's field. When you play a gear, it enters play under your control as its controller. Killing your Akshan does not return the gear to the opponent's field because the control-change effect from Akshan is no longer relevant to that specific instance of the card.

Step-by-Step Breakdown

1. Akshan's Effect: When you use Akshan's ability to steal an enemy gear, you gain control of it for as long as that specific Akshan remains on the board (FAQ 5396).
2. Ownership vs. Control: Ownership is permanent and determined by who brought the card to the game. Rule 107.6.f states that a card owned by a player can never be put into the hand of another player; if it would be, it is put into its owner's hand instead.
3. New Object: When a card moves from the board to a hand, it becomes a new object. Any previous effects (like Akshan's control-change) that were attached to it on the board cease to apply.
4. Playing the Gear: When you play a card, you become its controller. Because the gear is a new object once it has left and re-entered the board, it is no longer the same "stolen" object that was subject to Akshan's specific control-change effect.

Important Nuances

• Control: Control is a temporary state on the board. Unless an effect specifically states that the opponent retains control, you control the gear you played.
• Rule 107.6.f: This rule ensures that cards always return to their owner's hand, regardless of who controlled them on the board.

Note: I could not fully verify this ruling against the retrieved rules.