Remember, I'm using CustomNPCs for these, so I can't do that much because that mod has it's limits. And yes, I'll try adding Ch'throgg. Hey, did you guys check the mod list? I add new mods often. So please be welcome to suggest any non-OP mods for 1.7.10.
I'd rather you make your own that could have something to do with the End..... maybe an super powerful Ender Crystal who could be the remains of an ancient celestial being that almost killed the gods themselves long ago?
Let me give you an idea for this, Celestia, Ancient Being (Or Ancient Entity, pick the one you like better.)
Health:5000 (or 5500. Pick the one you like better.)
Attacks: Fires blocks of Pur-Pur Bricks. They do 54 damage (Try to suggest cool custom ender armor, and, I'll make a server. Someone suggest an arena and please help me build it! I'm not a good builder when it comes to giant things!) he can also spawn in Haunted Miners and Angry Endermen.
It also has dialog when it dies. Select the perfect dialog out of these three:
1.Nooo! My perfect dimension, the perfect life, you destroyed it all!
2.I'll be reborn, and brought back to life morons!
The model should be a giant Ender Crystal instead to make it unique
Celestia doesn't sound very intimidating.... maybe Dist-Orzai the Ur Destroyer
Creep's theme?...... No..... He should have legit final boss music so maybe a custom theme downloading from the internet such as the Polygon Man's theme.
He shouldn't really need an arena but rather a spawn item that is crafted from the crystals of creation.... one for Plution, Selyan, Luxon and Erebon.... each of these crystals of creation spawn in the bosses of their specific dimension for example... Elusive is fought in an Erebon dimension so the Erebon creation crystal would spawn him.... Dracyon is fought in a Selyan dimension so the Selyan creation crystal spawns him and etc.....
All 4 crystals would each drop an essence that can be used to make a custom recipe for the spawn item to spawn the final boss.
By the way, I can't do custom sounds/music. I will rename it Traxor'Ozi, the Ultragod. I can make custom items. I'll tell you what. There's going to be this special villager called a crafter. (I can't do custom crafting recipes but only trades.) Sadly, I Don't know if i can make the custom items do special things except weapons with enchantments. (I will TRY doing the legit theme. Say, how does Solaris Phase 2 music sound?) Btw here is the boss theme. How is that for the boss?
Deeplands no, Sorry, I kinda forgot some.
Lands of Lyletia, Celeve, (Yes, the nether is a yes. I did make a boss there.) (Free to make one for the end.)
I also did create one for Creeponia. Check at the top of pg 3.