House Martell. Loyal.
Event. Cost: 1.

Reaction: After you win an challenge by 5 or more STR, gain X power for your faction. X is the number of plot cards in your used pile. (Max 1 per challenge.)

Jean Tay
Core Set #119.

Link: Decklists

Doran's Game

This card seems like a game breaker in a Lannister Martell deck. Use The intrigue of both houses to gain card comtrol then on turn 6 or 7 when most of your plots are used and viola game over if you can secure 8 power in the turns building up. Iron throne and Lannister gold helps ensure dominance wins until you pull this off.

According to the rules in turn 7 the number of used plot cards in the game equals 0, so the bonus is 0 too. Page 15 of the rules - last paragraph in the section about plot cards. So on turn 1 you get 0, then +1 for each turn until turn 7 where you are screwed for two turns. — ptenteges 1
Cannot play this in Lannister Martell deck, this is Loyal. — SerNakata 7

Rules FAQ

RRG pg 15 "When a player reveals the final card of his or her plot deck, after all just revealed plot cards have entered play and all necessary 'When revealed' abilities have resolved, each plot card in that player's used pile is returned to his or her plot deck."

So with a standard 7-card plot deck, the most power you can gain will be 5 power on turn 6.