The Shadow of Death campaigns serve as a prequel to both Might and Magic VI: The Mandate of Heaven and Heroes III: The Restoration of Erathia. The storyline revolves around Sandro the Necromancer, who has recently arrived on the continent of Antagarich following the events of Heroes of Might and Magic II. Sandro begins a ten-year plot to reassemble two ancient and powerful necromantic artifacts. He uses illusionary magic to take the form of a living human, which he uses to disguise himself.

Sandro first convinces the sorceress Gem and barbarian Crag Hack to find the pieces of the two artifacts for him, promising rewards in return. Unaware of Sandro's true nature, they agree to aid him in wresting the pieces away from other necromancers. However, once secured by the unwitting heroes, the pieces are spirited away by Sandro without fulfilling his end of the bargain. He reassembles the pieces into two whole artifacts, the Cloak of the Undead King and the Armor of the Damned.

Sandro battles a Dungeon army in the Rise of the Necromancer campaign. With the Cloak and the Armor in his possession, Sandro battles the vengeful armies of his former warlock master, Ethric, and passes onward into the undead lands of Deyja. There, he vaults a puppet king, Finneas Vilmar, to the throne, attaining full political control of the undead lands. From there, he begins his plan to conquer the rest of the continent.

Some time later, amidst the war against the undead, the heroes Gem, Gelu, Yog and Crag Hack band together to combat the threat. They arrange to meet at the plains of Bragden, but are ambushed by Sandro himself and forced to flee. As they regroup, Yog recalls a task he performed earlier of dispensing the components of the Angelic Alliance, a mighty sword. The team of heroes decide to seek out the pieces of the sword and reassemble it. Succeeding, they push onward into Deyja, eventually cornering Sandro and defeating him. Afterwards, Gelu is chosen to become the Forest Guard's next captain, as referenced in Heroes of Might and Magic III: Armageddon's Blade. The heroes once again disperse the pieces of the necromantic artifacts as they part ways.

A final bonus campaign features Sandro after his defeat. The necromancer plots a second invasion, this time aimed squarely at Erathia. With the help of Lord Haart, he has King Nicolas Gryphonheart poisoned, and forms an alliance between Deyja, the Kreegans and Nighon against the human lands. However, he is tricked and imprisoned by his own puppet king, Finneas Vilmar, who then leads the invasion of Erathia which takes place during Heroes of Might and Magic III: The Restoration of Erathia.