The game is the third title set in the series' Ubisoft continuity, and acts as a prequel to Heroes of Might and Magic V, taking place in the fictional world of Ashan prior to the events of the game (producers Erwan Le Breton and Romain de Waubert have noted it as 40 years before the cycle of Heroes V and Dark Messiah of Might and Magic, averaging at 946 YSD in the timeline).

The game's story mode centers on its five main protagonists: Godric, Aidan, Anwen, Nadia and Fiona, who command knights, demons, elves, wizards and necromancers respectively. Godric and Anwen previously appeared as playable characters in Heroes V, while further returning characters shown in screenshots include Cyrus, Findan and Markal. The protagonists have been described as five lost children whose lives are shattered by "a mysterious Demon Lord with very sinister motives". This demon lord turns out to be Azh Rafir, Nadia's father, who had devised a mad scheme to use a powerful artifact known as the Blade of Binding to open the gates to the demon world of Sheogh and drown Ashan in chaos. He is shown to worship Urgash, the dragon of chaos, in Fiona's story. It is also shown, in Aidan's story, that Aidan had unknowingly taken the Blade of Binding. After the revelation that her own father had broken her life and those of her friends, a heartbroken Nadia decides to fight Azh Rafir in his demon lord form in the story's climax. After vanquishing him, she destroys the Blade of Binding and finally derails his scheme, bringing peace to Ashan.