Can a player use Gust to save a Kaisa (4 might unit) that has 3 damage and is being reduced to 3 might by Stupefy?

Ruling: No, the Kaisa cannot be saved by Gust in this scenario. The cleanup following Stupefy's resolution will kill the Kaisa before there is a window to play Gust.

Sequence:

• Stupefy resolves, reducing Kaisa to 3 might
• Cleanup immediately occurs, destroying the Kaisa (3 damage on a 3 might unit)
• No window exists to play Gust between Stupefy resolving and the cleanup

Nuances:

• The Kaisa is not 3 might until after Stupefy fully resolves, so Gust cannot target it beforehand
• If it was already a 3 might unit with 2 damage and Stupefy was incoming, Gust could save it (by bouncing it before Stupefy resolves)