I'll tell you everything; I've been developing this concept for a year now...
And all the races are unique and different...
The only problem is with the Elementals; it's very difficult to come up with units for them, but I'll try...
And regarding the imagination... it's just an idea for now, but believe me, it's much more realistic than the races offered in Ascension...

Added 5 minutes ago
And I haven't seen a decaying tree used as a city anywhere else... Elves live in forests on a giant tree, and the Dark Elves can live on the same type of tree, but old and abandoned...

Added 24 minutes ago
I don't have much time to write about everything right now, but I'll choose a day and tell you about everyone in detail.

Added 39 minutes ago
Faction - City - Color

Empire - Castle
Forest Brotherhood - Tree
Mountain Clans - Bastion
Sorcerer's Cult - Oasis
Celestial Kingdom - Temple
Elementals
Ancient Tribes - Pyramid
Horde - Asylum
Sea Kingdom - Island
Night Brotherhood - Dungeon
Necropolis
Inferno