I like this card a lot for Wall decks, specifically if you're running Thoren Smallwood or Ser Denys Mallister. Normally you don't really care about actually winning challenges, you just want to defend every challenge. But this card lets you choose to win a challenge and gain power while doing it. Or it lets you beef up Qhorin and let him take a swing at someone attacking you and kill a lot more powerful character during the challenge. This is a very strong card when used in the right circumstances.
Stronghold. The North.
Action: Kneel Abandoned Stronghold to choose a defending character. Until the end of the challenge, that character gets +X STR. X is the number of Builder characters you control.