Mordor

The Uruk-hai belonged to Saruman, but later, on Sauron's orders, he sent several squads of these new orcs to him. As for the rest, you're right; it would be better to add them instead of leaving half of the race from Heroes 3 out, if you're going to change things, do it completely. By the way, how did the Beornings end up in Mordor?
P.S. In my opinion, it's not worth including Perumov. After Tolkien's death, he brazenly invented a lot of things, and didn't even bother to write them well (although he certainly can), he came up with a lot of things, and the scale he used was even greater than Tolkien's. It's as if everything is even more serious and terrible. I don't think that's right.