The plot of Heroes of Might and Magic V.

Next on the list are the dark elves; the campaign is deadly boring, though that's just my IMHO. We start as an old acquaintance, Agrail. Only now he has changed his name to Railag, and in general, he only resembles his old self in voice (and the lizard :) ). If he was previously the Demon Lord, now he's just a Warlock. Railag is not satisfied with the state of affairs (for some reason in Heroes 5, everyone is dissatisfied with something :) ) and he decides to seize power somehow. And lo and behold, right at that time, a tournament began for the position of head of the Shadow Clan. Anyone can participate! The tournament basically consists of gathering an army and then surviving gladiator battles—all heroes are teleported to one place where the brawl begins. Railag naturally wins. The second mission—Railag wanted to conquer the other clans, so he goes to Malsara (one of the daughters of Mallassa, the dragon-god of the dark elves). She suggests nothing original, specifically advising him to build the Mother of Darkness (Tear of Ashan) in his city, as well as to conquer the Shadow Shards clan by force. Which is what we do. The third mission is one of the hardest in the original. The goal is as old as time—this time you need to conquer the Grim Hearts clan. Railag also has an additional motive to do this, as the Grim Hearts have formed an alliance with the demons. After our hero completed the assigned task, he was fortunate enough to find out that the Overlord is preparing a foray to capture Isabel. In the fourth mission, Railag rushes straight to Isabel, and the shortest path lies through Sheo, where he arrives at the end of the fourth mission. In the fifth, our goal is to save Isabel, who together with Markel is heading to the resting place of Nicholas, from an Inferno hero who was sent to capture the queen. Railag saved her from captivity and also suggested that Isabel abandon the resurrection plan, but Markel was against it, so the elf failed.
The fifth campaign is the light elves.
Our hero is Faendael, a master of idiotic poems. In the first mission, he defends the borders of Irollan from the encroaching Necromancer. In the second, he decides to secure the support of the most powerful creatures of the elves—the emerald dragons—while killing demons that have leaked into Irollan. In the third mission, Syris-Talla, the elven capital, comes under attack by Necromancers and is even captured. Faendael successfully recaptures it, fortifies it, and then rescues two elven generals from captivity. In the fourth mission, Faendael sails to Tiera, however, he is too late—Tiera has already been overrun by demons. After this, he will also have to defeat Biara (who will slip away). As for why the demons killed Tiera, I've somehow forgotten :) The fifth mission is quite long, but there's not much to tell about it—our goal is to take down Nicholas the vampire, who is ravaging the elven lands. After the final fight with him, there is a cutscene—Faendael apologizes to Nicholas (they were friends, after all), but says he must kill him. The ex-king does not object; he has long been fed up with his current existence.
The last campaign is the Mages. We play as Zehir, son of Cyrus, current ruler of the Silver Cities. In the first mission, he follows Lenin's order—study, study, and study again! Our goal is to level up to 10 and take a city from the Necromancer. The second mission is essentially the reverse of the third Necromancer mission—you need to retake the cities captured by Markel, including Al-Saphir. The third mission continues the madness—you have to retake the cities of the Griffin Empire from Markel, free Godric, meet with Faendael, and the three of them kill Markel. I don't understand how Zehir was able to gather an army from a practically destroyed state capable of dealing so easily with Markel and all his conquests. Be that as it may, in the cutscene, Markel theatrically declaims, like, kill me, I'll resurrect anyway, I'm a Necromancer, ha-ha-ha. His outpouring of words is interrupted by a fireball launched by Zehir, which incinerated Markel to ashes. The fourth mission—capture Isabel and perform a ritual that will protect her from Kha-Belekh (or something like that). Toward the end of this mission, Railag and Shadia join us. We capture Isabel (she doesn't want to go voluntarily), and in a cutscene, we perform the ritual, during which Biara appears and carries Isabel away with her to Sheo (Kha-Belekh is an idiot, couldn't he just do that right away? No, he had to send heroes to intercept. Poor guy :) ). The fifth mission, the last one, takes place in the campaign of 4 heroes—Zehir, Godric, Faendael, and Railag; first, they take turns defeating Biara, and then the Overlord himself (well, they just retreat, rather than die). A problem is revealed—the heroes were late, Kha-Belekh has already done something... terrible to Isabel. And now the prophecy of the Dark Messiah, who will plunge the world into the abyss of Chaos, and blah-blah-blah, must be fulfilled. Jumping ahead, I'll say that the prophecy came true, as told to us by the wonderful game Dark Messiah of Might and Magic. That's how it is.