I think this is quite promising. We should be able to use most, if not all of it. I can't say for sure because it depends on how the lore for some other factions pans out. It doesn't contradict anything that we already have, though we have very little at the moment.My take on the Necromancers.
They were relatively rare individuals - most of them were hermits, travelling the world. Nobody remembers who became the first one, there're different legends about it (but no debate, as Necros are not a thing commonly discussed). The most popular one tolds a story of a caretaker (former Wizard) named Nethos. He was a humble, but troubled man: all of his family died due to different reasons and he buried them himself as well as countless others. His village's graveyard was located in the forest, and after some time, he started noticing that plants around him started to wither. He became something akine to Vampire, sucking the life energy from every living things around him. First it were mere plants, but with more buried dead his powers started to grow and worked on other creatures as well. The villagers quickly understood what's going on, and prepared to burn the caretaker, only to realise that they can't even get close to him withour meeting death - such was Nethos' aura. Nethos himself was terrified by his curse and decided to commit suicide by jumping off the nearby cliffs, located to far from the graveyard. But death rejected him. The energies of the dead that he sucked out flowed through him and withered his flesh. With aghast eyes he awoke from his near decade slumber and rised as a Lich, the Undead Wizard. From that time on he tried to understood what unlock those powers within him, how he became a Lich and later he dedicated himself to helping others with similar curse.
But time passed, and now 9 powerful Necromancers united their powers to establish a foothold far to the south, in the region called Black Sands. There, they built a Necro academy and ressurected the Cursed Legion... to once and for all end the Crusades declared on them.
But off with those old myths and fireside tails. To become a Necromancer, a creature must witness a death. More death you witness, stronger you become, to the point that Necro power may work automatically. This person becomes an "accumulator"/"attractor" of sad feelings, grief etc and his abilities work on sansation level - controlling death energies.
Well, how controling. If Wizards act as "transformers", Necromancers act as "suckers". They suck the energy of living beings, but they cannot store it within themselves and - the most important part - they can't suck a part of energy. Either no energy at all, or they suck it dry and effectively kill the target. Also, most of the Necromancers can't effectively control those enrgies - they're present around them, accumulate and after some time start to flow through the Necro, turning him into an Undead. Becoming Undead unlocks fully the Intellect layer, and only then a Necromancer gains complete control over death energies. He now can turn off/on his aura, direct the energy to erode things, use it to animate higher forms of Undead. There's a drawback though - the Emotion layer is shut down for them.
Ofc the Necromancers trademark ability is the Necromancy. There're 2 ways of it.
The living Necromancers, acolytes or "cursed ones", must use the bloodcurdling rituals to animate the skeletons. The blood of the victims becomes a force that joints the skeleton parts together and keeps them from falling apart. To rise Zombies, they need to suck a living thing with all of its energy and left the corpse inside special formula. The body then rises again, animated by the desire to regain it's energy back. That's the reason why they eat mortals.
The Undead Necros master the death energy and can play with them. They no longer need ingredients to rise the dead, and they also learn the rituals the enable them to rise more than mere skeletons and zombies...
That's just a draft, not very thougth out. Contains grammatical errors. I hope it doesn't conflict with the existing lore.
Waiting for opinions ^_^
I'll post some guidelines for further faction design, including lore writing, later today. I just have a few other errands to take care of first...