If I target a 2 Might unit with Gust at Abandoned Hall, and my opponent responds with Combat Experience targeting the same unit, does the unit receive +1 Might from Abandoned Hall's trigger before Gust resolves?

Ruling: Yes. When Combat Experience finishes resolving, it triggers Abandoned Hall immediately, placing that trigger on the chain above the still-unresolved Gust. The Abandoned Hall trigger resolves next, giving the unit +1 Might (bringing it to 4 total), before Gust attempts to resolve. Since the unit now has 4 Might, it is no longer a legal target for Gust, and Gust's effect fails.

Sequence:

• Gust is played targeting the 2 Might unit
• Combat Experience is played in response, targeting the same unit
• Combat Experience resolves, giving the unit +1 Might (now 3 Might)
• Abandoned Hall triggers for the opponent and is placed on the chain
• Abandoned Hall trigger resolves, giving the unit another +1 Might (now 4 Might)
• Gust resolves but fails because the target now has 4 Might
• Abandoned Hall triggers for you and is placed on the chain

Nuances:

• If Combat Experience targeted a different unit, the original target would only receive +1 Might from Abandoned Hall (3 total) and would still be returned to hand by Gust.
• Triggered abilities from "when a player plays a spell" effects are placed on the chain after that spell completely finishes resolving.