Can cards be played during chain resolution, and specifically can an opponent use Gust to save Kai'sa after Stupefy resolves if both Hextech Ray and Stupefy are on the same chain?

Ruling: During chain resolution, players can add reactions to the chain with priority passing between players. However, in the specific example, if Hextech Ray and Stupefy are both on the same chain (Ray resolves first, then Stupefy), the opponent cannot use Gust to save Kai'sa because cleanup occurs immediately after Stupefy resolves, destroying Kai'sa before any player gains priority to play cards.

Sequence:

• Hextech Ray and Stupefy are both added to the chain
• Stupefy resolves first (top of chain)
• Cleanup occurs immediately after Stupefy resolves
• Kai'sa dies during cleanup (damage marked ≥ her new reduced Might)
• No opportunity to play Gust before Kai'sa dies

Nuances:

• If Hextech Ray resolves completely and the chain empties, priority automatically passes to the opponent, giving them a chance to start a new chain with Gust before Stupefy is played
• The key is keeping both effects on the same chain so cleanup happens immediately after the stat reduction