If you look at the initial idea, the color examples in the screenshots:
Here's what the dragons look like:
https://c2n.me/48GTLdT - bone dragon
https://c2n.me/48GTMeI - spectral dragon
https://c2n.me/48GTJXk - blood dragon
https://c2n.me/48GTObs - dracolich
1) Fallen Dragon - a typical medieval dragon, burns villages and sleeps on a mountain of gold, its connection to the spirit world is broken, and now it draws power from artifacts and gold.
2) Blood Dragon - more like undead, possesses vampirism, the situation is similar, but it feeds on life force; the idea is based on the dragons from the mission about Erivell, where they had to sacrifice 100 elves.
3) ???? - a dragon that feeds on mana, it drains mana at the beginning of the battle and when attacking mages.
I'm refining the Nephilim; now they have larger wings to make them look more massive