If Tryndamere is moved to an open Battlefield as a defender using Ride the Wind, wins the showdown, and conquers, does his ability trigger to gain an additional point since conquering happened during an attack?

Ruling: No, Tryndamere's ability does not trigger in this scenario because Tryndamere was a defender, not an attacker. The ability specifically requires conquering during "an attack" which refers to being the attacker.

Nuances:

• The ability triggers at the end of showdown when conquering happens, which creates timing ambiguity since attacker/defender designations are cleared during combat cleanup
• Tryndamere's ability depends on tracking past game state (both excess damage and attacker status) in ways not explicitly supported by the rules as written