The wording on the Martell Attachment 'Taste for Blood' came up in a game the other day for our meta.

Would the character only recieve power if a challenge is defended (by any character I control) or does losing an undefended (by me the defender) challenge also count as a loss and a power on the character?

Thanks!

"Response: After you lose a challenge as the defender, attached character claims 1 power. "

You are the defending player, even if you have no defending characters.

There are no "undefended" challenges -- only UNOPPOSED challenges.

kauai1964 said:

Now I see the difference, I tougth taht you must defend with character if you wanna trigger abilietis who starts "with lose challenge as defender",

but if I understand it correctly it means that this can you trigger only when you are the defending player, and "when you lose a challenge "can trigger even when you lose as attacker, Is this correct understanding ?

Correct. If you are the one being attached, you are the defending player. It wouldn't matter if it was opposed or not, if you lose the challenge, you lost as the defender and get to trigger any such "after you lose a challenge" or "lose a challenge as the defender".

Another scenario would be the Seige of Winterfell agenda that lets you claim 2 power any time you win a MIL challenge. Since there is not requirement of "attacker" or "defender" you can claim this power after winning on either side of a MIL challenge.