When defending with Master Yi's +2 might bonus and playing a Challenge Action spell during a showdown, does Challenge count only the unit's base might or does it include the defending bonuses?

Ruling: The might increase from defending bonuses counts. The unit has the increased might while the showdown is ongoing, so Challenge uses that total might.

Nuances:

• The +2 from Master Yi is technically not a "buff" in game terminology, though it functions as a might increase during defense