The climactic battle during the Return of the King. Aragorn and his friends have been spirited away and won't be joining. But coming to the aid of the White City, instead of Rohan and the Rohirrim; the army now consists of Aslan's and the White Witch's army from Chronicles of Narnia - including the kids, Aslan and the Witch. Does this army change the course of the battle? They have to contend with the siege army of orcs and trolls; then the corsairs with their giant elephants. How does it go?
So you got a powerful witch, minotaurs, giants, and Phoenix replacing some dudes with horses? Legolas is the only notable loss, but I think they can manage
Narnia uber-stomps the armies of Mordor. Shoot, some of them are centaurs, so they have cavalry plus a collection of Heroes of Might and Magic 3 creatures with no morale penalties at their disposal.
Also, you now have Aslan in the place of Théoden and the witch in place of someone like Eomer.
Mordor is done; the men of the east on elephants make it a bit more interesting, but Narnia could handle them without any Army of the Dead backup, IMO.
I have to disagree. Sure the Narnia armies have some good super units but there was barely enough of them to fill that field. I'm worried the sheer size of mordor will overwhelm them. Not to mention the mass of cave and mountain trolls that are even greater than some of Narnia's bigger units. Phoenix would be handy though tbh.
The only magic I'm aware of is the White Witch - and she'd likely be a glass cannon; the rest of Narnia, while being magical beasts, were mostly physical type attacks (melee, range). I'd say Narnia has aerial superiority though.