I like the idea of the quest, but it seems to me that the reward will only have limited use. It's fine for countering cards which take away your health or quanta or cause you to spend extra quanta (like Rewind), but I can't see how it'd be much use against most cards. How would gaining 5 HP and 5 quanta be in any way beneficial against Fire Shield, for example? Or the Shard of Sacrifice?
I'm not sure what the reward should be, and I like the idea of having something added to your mark, but I think that this current idea is far more limited than it initially seems.