My playgroup has been playing with the expansion for a couple months now, and the same question keeps popping up with this card. Card text reads: "You may discard any number of your available Power tokens to increase the combat strength of this card by the number of Power tokens discarded."
Do you have to declare the number of tokens you are using when the card is flipped?
Example: Greyjoy is attacking Lannister and combat strength going into the House cards is tied, 2 to 2. Greyjoy has 10 Power tokens and Lannister has all his house cards. Lannister decides to play Cerci with 1 Combat strength and Greyjoy plays Aeron. Is Greyjoy able to see the Lanister card, then discard 2 tokens, or discard tokens simultaneous with the flip of the cards?