How long do might increases from cards like Decisive Strike last, especially when used during a showdown on an opponent's turn?

Ruling: Might increases and decreases last for the duration specified on the card. When a card says "this turn," it lasts until the end of the current turn (the turn during which the effect was created), not until the end of your next turn.

Sequence:

• If you use an action/reaction that grants +2 might "this turn" during your opponent's turn (such as during a showdown), the might increase lasts until the end of your opponent's turn
• The might increase is cleared at the end of that current turn, before your next turn begins
• A showdown is not itself a turn; it occurs within a turn

Nuances:

• "Buffs" are a specific game mechanic that are permanent game objects lasting until removed or spent by effect
• Might increases/decreases are different from buffs and last only as long as specified on the card
• Some effects like assault only last as long as the condition is true
• Effects that say "this turn" always refer to the current turn in which they were played