Jailer’s goal was to break free, get all sigils and than use mysterious power of the First Ones to rewrite all of creation into version he is the main figure head and doesnt have to serve anyone. Specially some flawed Purpose.
It’s at the same time reason why Void Lords dont like him (and therefore his forces of death), they dont want to be rewritten. They just want steady source of souls and realities to consume. Which also makes them plain evil. I dont recall them being more sophisticated than that. Only eat and replace it with void. Oh and twist some of the useful puppets into their monsters.
Cult of Damned WotLK version belived that if everyone and everything was bound to serve one true king there would be true peace and unity everlasting. Since as undead (which they saw as being elevated) everyone would be immortal. After SL they shifted from worshipping Lich King to Zoval.
Old Gods were made with purpose of infecting and corrupting worlds they stumble upon. Preferable ones with powerful World Soul inside so that it may bore a void-titan. What they werent told it seems was to play nice togather as they waged wars with each other. Yet aside for Xalatath they were always focused on their prime directive. N’zoth after being freed wanted to corrupt world and it’s soul via forge of origination. What Xalatath is up to is anyones guess. Myabe she’s plotting her own way to come back with an army to conquer Azeroth?
Twilight Hammer was a cult. They’ve worshipped old gods and belived their point of view on reality - that Titans are oppressive tyrants who violate natural order with their own flawed artificial version of it. As a cult they combined masses of expendable broken people, the perfect type for any cult and fewer power hungry individuals who also belived void take on all things but at the same time whised for some reward for their loyal service.
Druid of the flame were bitter sect of druids who all have lost something that was dear to them in one form or another. For Fandral Staghelm it was his son who was torn in half during War of Shifting Sands. He blamed Malfurion for this especialy after Xavius through visions, in which he appeared as his lost son, convinced him of this. He wanted revenge. After his plans in classic to keep Malfurion stuck asleep in Emerald Nightmare failed he was inprisoned by the Wardens. During cata he was released by Twilight Hammer alied green dragon and togather they escaped into Firelands where they ascended into elemental forms. In their bitternes Druids of the Flame wanted to see the whole world burn.
Godfrey was radical conservatists and scheming politician who hated worgens. It didnt matter to him if they were feral or not. He couldnt stand the idea that king himself was cursed aswell and rebelled. After death he cooperated with the Forsaken to clear his homeland of worgens, in his own words “better dead than worgen”.
Xavius had long history with Malfurion. He was loyal right hand man to Azshara and first night elf to become demon. He was defeated by Malfurion and as punishment to think on his actions cursed into a sentient tree. After sundering one of the old gods found him and gave him a chance for revenge on archdruid by sending him into the emerald dream from where he can oversee the growth of emerald nightmare. From there he attempted few plans to get Malfurion (and whole world too) but was stopped. In legion boosted with new power he broke free from his tree form and yet again attempted to get his revenge.
Emerald nightmare was simply void incursion into the emerald dream. Made possible when one of the great portal trees roots touched inprisoned Yogg’saron.
Elisande using her time magic viewed all potential futures for her people and the only one where she wasnt killed and her city burned was the one where she served the Legion. It is speculated that something or someone influenced her visions. Everything after that was just her trying to stay in power so that she can prorect her people and herself. When killed she realises that maybe we are the best option for her people and gives us her blessing to kill off Guldan.
Xera wasnt evil she had problem with respecting other people choices especially if they interfered with her own plans. Thats why she attempted to lightforge Illidan regardless of his whishes. It’s the alternative Dreanor Xera that might be more “evil” since she ordered Draenei to force convert everyone to worship the light.
Horde in BfA had some solid reasons to start the war. Were they too slow to act against Sylvanas? That’s complex question - how do we place the concept of honor and oaths in it?
Helya have rather sad story. She was almost daughter figure to Odyn. Skilled in magics, when Titan forged fought the Old God controlled elementals it was her who came up with idea to create elemental planes - special dimensions where elementals would be isolated from matrial plane. Thanks to her they wouldnt be able to simply reform as a new elemental when killed. Instead stuck in their plane. Much later, after war was won she helped Odyn create to procedure that would allow him to make valkyrs (he didnt want his now affected by curse of flesh soldiers to go into Shadowlands). He insisted that she would be the first to become one despite her many protests. Being forced into this new form filled her with hatred towards her “master”. When Odyn whished for her to create him his own plane to which his dead soldiers would ascend she tricked him. She ceated the plane but did it same way she did elemental planes. Once inside Odyn was unable to leave. After that she created her own valkyrs and decied to steal Vyrkul souls form him. Turning them into her Kvaldir instead to mock and punish him further.
Drust were some off sub race of Vyrkul origin. They specialised in magics of nature and death. They were also, just like orignal Vyrkul very unwelcoming of outsiders. Using their magic of death they created themselves their own realm of death - Thros to preserve their own souls in case of death. Some time later human colonists came to their shores, as expected Drust reaction was to butcher the civilians and make a sport of it. War with humans began. Despite their dark magic and superior strenght they were beaten and killed almost to the last (they wouldnt surender). But not all Drust fought the humans. Thronspeakers were more paceful and managed to coexist with new habitants. While the dead Drust were stuck in that realm of theirs with nobody left alive to summon their souls back into living world and unable to pass into afterlife. In SL they managed to invade Ardenweald from Thros and hope to use it’s reincarnation powers to bring themselves back to life. Probably to continue their fight against Kul Tirana.
Bwonsomdi isn’t evil, not pristine like Anduin but not evil. He saved souls of his followers from the Maw.
Sylvanas shares Zoval sentiment that current system of life, death and Purpose is flawed and oppressive and just like him whises to rewrite everything into new order. Problem is Zoval used her serving trauma to show himself in similar position to her to gain her trust. Created to serve one purpose and than bound for wanting his freedome. What he didnt mention was that the reality he wants to bring is not about freedome but even worse version of current one with him as supreme ruler and one only god.