Gain control of target spell. You may choose new targets for it. (If that spell becomes a permanent, it enters the battlefield under your control.)
You may change any or none of the spellâ€™s targets. If you change a target, you must choose a legal target for the spell. If you canâ€™t, you must leave the target unchanged (even if the current target is illegal). Notably, if you were originally chosen as a â€œtarget opponentâ€ for a spell you gain control with Aethersnatch, you are now an illegal target as you arenâ€™t your own opponent.
If you gain control of an instant or sorcery spell, it will be put into its ownerâ€™s graveyard as it resolves.
If you gain control of a commander spell, the commanderâ€™s owner chooses whether to put it in the command zone if it later leaves the battlefield.
Combat damage dealt by a commander is tracked without regard to who controlled the commander at the time it dealt damage. For example, say a commander deals 10 combat damage to a player, leaves the battlefield, is recast, and you gain control of it with Aethersnatch. If it deals another 11 combat damage to that same player, they will lose the game.
Aethersnatch can target any spell, even one without targets.