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.
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.