Of the events that shuffle beneficial cards into the encounter deck, this one is my favorite (the other options at the time of this writing being Ranger Summons, Flight to the Sea, and Tom Bombadillo!). There are several reasons for this:

1. Free to play. With the others, you are paying up to 2 resources for a benefit that you likely might never see! Unless you are just swimming in resources or have a gambling problem, this should give you pause. Is this really the best way to spend those resources? Of course, the more players there are in the game, the more likely the gamble will pay off. But in a solo game, those other cards are close to unplayable. Here at least you are only paying the cost of a card (not insignificant, which leads me to my to my next point...)
2. The card actually does something useful beyond shuffling something into the encounter deck. That makes the encounter card more of a bonus if you draw it, rather than its only effect. Now normally, returning an ally to your hand would be a downside, but an eagle deck has several reasons for wanting this to happen:
   • Triggering Meneldor or Descendant of Thorondor up to two more times.
   • Triggering Gwaihir again (not as crazy as it sounds if you're running Radagast's Staff and/or Hirgon). Combos well with the previous eagle cards.
   • Return Vassal of the Windlord to your hand after applying his damage, but before he gets discarded. This never used to be possible in the early days of the game, but works now thanks to the revised timing structure in the online rules reference (confirmed by Caleb). There is a player action window between 6.8.3 "Determine combat damage" and 6.8.4 "Player attack ends". Similarly for Winged Guardian and the action window between 6.4.3 and 6.4.4 (the attack will still be defended).
   • Move an already exhausted eagle underneath Eagles of the Misty Mountains to boost his stats. This can be triggered mid-attack even.
   • Return the spoiled Wilyador (The Land of Sorrow) to your hand if you can't/don't want to pay his upkeep, or as a guaranteed way to trigger Radagast's Response ability next turn.
   • Ready the spoiled Gwaihir hero (The Land of Sorrow). This combos with any of the above, getting even more value out of a single card.
3. Eagle of the North kicks serious butt. Don't get me wrong, the other encounter cards are also great, but this one is the best of the bunch in my opinion. When you factor in the cost, then there's no contest. Tom Bombadil is amazing (especially since since he doesn't have "surge"), but you only get him for one round. Wind from the Sea also lacks surge, but is very hit-or-miss without scrying. Ranger of the North is a terrific ally (especially in multiplayer), having stats comparable to Eagle of the North. But what puts Eagle of the North over the edge for me is the When Revealed effect. You are both getting a permanent ally and a killer one-time effect. Also, for me, this one best captures that "deus ex machina" feel when out of nowhere an eagle swoops down and carries off that Mumak you thought for sure was going to grind you into paste.

The only bad thing about this card is that it's the final nail in the coffin for Meneldor's Flight. The only possible reason to include the latter in your deck over this one would be if you want to use Háma or Book of Eldacar to replay it, but that's a real stretch. I suppose if you're using the new Gwaihir hero then maybe you'd want 3 x of both cards? But otherwise, Meneldor's Flight is pretty much a coaster. Which is a shame, since printing cards that are strictly better than previous ones limits deckbuilding choices.

For me, this card is great. I really enjoy the idea of adding your own player cards to the encounter deck so as soon as I saw this card, I knew I had to put it in my eagle deck.

To play it you have to bring a eagle ally from play back into your hand. This could be quite expensive in most situations but could help for some of the eagles. If you use it on Descendant of Thorondor or Meneldor or even Gwaihir, then you can get more uses out of their abilities. So, if you have loads of reasources then this could be worth it, but you would probably want to use it on some of the more cheaper eagles like Vassal of the Windlord and Winged Guardian.

One way to "cheat" the cost is to Sneak Attack or Gwaihir an eagle ally in and then use this card on it.

The Eagle of the North ally itself is actually quite good. With the 2 and 3, it gives you some choices on what you want to do with it. You can quest or you can use him for a bit of attack. You'll probable want to quest with him cuz eagles have very low . You can also give him to another player who is in trouble in combat to help them out.

The Eagle of the North's ability is quite useful. Not because it gets rid of an enemy so you don't have to fight it, but rather because it gets rid of some of the in the staging area. Eagles have no problem dealing with enemies as they are very combat-powerful, but they can't do much during the quest phase.

This card is a card that you could think is worth it or.... not so much. For me, it's worth it because I like playing with gimmicks like this as I find them to be quite fun to use, but I'm sure there are better cards to include in you deck.