Rider of the Mark, at first glance, seems like a reliable way to waste spirit resources. He is however not a bad quester, has an extra hit point, and has built in shadow cancellation. If you don't quest with him and use his ability, he can swing for one to help kill that shadow-less enemy. One thing to note is that since the shadow card is discarded, you can get around effects like Smaug's and those pesky Wargs' that reference different things on the shadow card itself.
Rider of the Mark
Action: Spend 1 resource to give control of Rider of the Mark to another player. (Limit once per round.)
Response: After Rider of the Mark changes control, discard a shadow card dealt to an enemy you are engaged with.
Road to Rivendell #33. Spirit.