If a unit that initiated a showdown is removed during the showdown (via a combat trick), can the opponent still play spells before the showdown ends and units heal?

Ruling: Yes, the opponent can still play spells like Hextech Ray before the showdown ends. The showdown does not end until all players pass Focus, even if one player has no units remaining in the showdown.

Sequence:

• Kai'Sa moves to Targon's Peak, initiating showdown
• Kai'Sa's controller passes priority
• Opponent plays Challenge in response
• Challenge resolves, Kai'Sa is removed
• Players continue passing priority in Focus
• Opponent can play Hextech Ray before all players pass
• Once all players pass Focus, showdown ends and remaining units heal