How many times can you spend power for Draven, Vanquisher's ability per combat?

Ruling: You can spend 1 power per combat when Draven attacks or defends. You may choose to spend the power or not.

Nuances:

• If Draven is moved to a contested battlefield mid-combat (e.g., via Ride the Wind), his "when I attack/defend" trigger activates when he is first assigned his role in that combat.
• If moved to an open Showdown (not yet in Combat), Draven waits until the Showdown concludes and Combat is initiated, then his trigger occurs on the Initial Chain when assigned as Attacker or Defender.