Éowyn is just a placeholder for Tactics Éowyn here!
Essentially, it combines the questing power of Spirit with the fighting prowess of Tactics. Éowyn's ability can be handy early on to get rid of a nasty enemy, or later, depending on the scenario. With a low starting Threat of 18 (after the reduction during setup) the deck can play Secrecy cards, and has Recourceful and the Celduin Traveler to make use of that. There is also plenty of Threat reduction, but mostly those are there to cover the costs of Frodo and Gandalf.
Frodo will be the main defender. Early on the Derndingle Warriors can help out, and there is Feint for those times, but later he should be fine with some Ring Mails and Unexpected Courage. Glorfindel with Blade/Dagger should do plenty damage on his own, and Éowyn is there for that one big hit. And then there are Gandalf and Treebeard, of course.
In the latest version, I have removed Herugrim now, since it's just not necessary and I would rather keep the Unexpected Courage for Frodo.
The deck should work well for solo play, but also for multiplayer games.