Most of what needs to be said has already been said here, but I wanted to add two more targets: Prince Imrahil and Haleth. I'd also note that this attachment is more likely to find a juicy target when you're playing multiplayer, especially 4P.

63
does not work for imrahil as soon he becomes hero. (and thats the maingoal if including that version) —

A really good ally with a high-risk, high-reward text. And allies with two Willpower for two resources are always great, even if most of them have Spirit as a home.

For its Action, it is specially good in a deck that feeds its discard pile, like Noldor, Caldara, or any deck with key cards that should not be lost, like Council of the Wise. For the passive ability, I understand it thematically, losing the game if Frodo dies - for which it's nice to have two hit points! But I don't understand the thematic excuse for his action. Is Frodo now a Necromancer, resurrecting dead allies? Is he delving into the ancient writings of Minas Tirith like Gandalf? Why can he retrieve cards from the discard pile?

Anyway, a great card that even allows you to use the Spi ally Sam Gamgee. And you can always nullify the risk by returning him to your hand after using his Action with effects like Lily Cotton - even if it doesn't allow you to use his action again.

1
As a once-per-game effect, it was meant to reference the important moment of Frodo picking up the One Ring, which Bilbo had "discarded", rather than some sort of necromancy/mining effect. —

I like his stats, he can be used at questing or defending. But I don´t see many options to discards allys from play. Maybe someone can help.

At first glance I wanted to combine him with Eowyn and Theoden in a mono spirit deck.

Rohan has a lot of cards that either self-discard (Grimbold, Westfold Outrider, Riddermark's Finest etc) or events to discard allies (Ride to Ruin, Worthy of Remembrance). Morwen is also a perfect complement for Thengel's ability. Also worth nothing that Thengel effect is not limited to Rohan allies, it can help with many Eagles allies or some Beorning ones. —