The plot of Heroes of Might and Magic V.

It all starts with the interrupted wedding of Queen Isabel and the invasion of demons, which is essentially what the plot revolves around. King Nicholas (Isabel's husband) is fighting on the borders, and Sir Godric has embarked on a diplomatic mission to the Silver Cities to seek help. Godric is refused, and Isabel decides to raise a militia, which she does while also killing demons. In the fourth mission, she is ambushed by the demon lord Agrael, who captures her. It is also revealed that Isabel's friend has died (I don't remember her name). During their conversation, it becomes clear that Agrael has fallen in love with the queen. Perhaps that's why the Dungeon where Isabel is held is not very well guarded... Godric frees Isabel in the fifth mission, and after that, they together repel Agrael's attacks. Eventually, Godric decides to rush to Nicholas to ask for help. The king comes to their aid, but Agrael kills him, and then flees. There is a tearful scene here – Isabel talks to the dying Nicholas. It turns out there is a problem – there is no heir! The second campaign is dedicated to Agrael. Throughout the first mission, he has one task – to escape from the enraged Godric. After escaping, in the second mission, Agrael learns that the demon lord has found out about his betrayal (he didn't deliver the queen) and sends one of the demons to intercept him. Also, for some reason, Agrael needs the heart of a griffin (I don't remember why anymore). After killing the demon, the spirit of the ancient hero Tieru appears, who calls him to sail to his island, promising to explain everything later. There is nothing else to do – Agrael has to fight his way through the Elven lands to the port in order to sail away on a ship at the end of the fourth mission. In the last mission, Agrael is actually looking for Tieru – there are many islands. When they meet, Tieru makes Agrael an offer he cannot refuse – to shed his demonic essence and cease to be a demon. The next campaign is about the Necromancer. Should I continue?
The plot of the fifth game is not connected to either Heroes 3 or the other games.