Right then. Evil, Different, Monsters coming up.
My first thought on seeing you had The Witch King was an Angmar force; it doesn't tie that thematically to the Fallen Realms, but as a standalone you can port over The WK to start, which is handy. And as for different, I think a spirit-heavy forces might be a fun one, lots of conversion potential (anyting painted glowy=Spectre

)
So how about this:
The Witch King, Horse, 14 Will, 2 Might/Fate: 120
10 Orc Warriors, Shield: 60
10 Orc Warriors, Spear: 60
10 Spectres: 150
Burdhur, Troll Chieftain: 110
500 on the dot. Orcs for numbers, 10 Spectres gives you a very good chance of moving half a dozen enemy models a turn (basically mini-Compels), and Burdhur can smash stuff up while providing some Might as well (and he's one of the coolest models in the range to boot!)
Moria would be best suited to a Horde list, to complement the lack of numbers in your Easterling list. Something like this:
Gundabad Blackshield Shaman: 50
Moria Goblin Shaman: 45
5 Blackshields: 40
5 Blackshields with Spear: 45
15 Goblins with Shield: 75
15 Goblins with Spear: 75
Cave Troll, Chain: 85
Cave Troll, Chain: 85
500 again. Plenty of bodies, a fair bit of magic to throw around (I suggest Challened Fury from the
MG Shaman in the middle of the blackshields, and the Blackshield shaman hides behind your line to either pop out and Tremor the enemy line or to Shatter someone's magic sword. He could also be swapped out for a Captain if you want a little more Might.