Its name means 'castle of dread' in elvish, and the very utterance of that name conjures images of horror and death. Erôn-Mored was originally built by the Dark-Elves during the late Second Age upon on a small island in the center of the Sür. Today, the castle is home to the seven Zûl; the most powerful servants of Sorimmar.

The castle was originally built as a laboratory, where the Dark-Elves conducted foul and terrifying experiments on men, elves, and beasts. These experiments led to the terrible pollution of the lake that surrounded the island, and it became accessible only by special metal-hulled ferries that could withstand the acidic nature of the waters.

After the fall of Drotharë and the end of the War of Wrath, the Dark-Elves abandoned the castle and its many dark secrets. It was soon taken over by Alokkair, who had been an apprentice of the Dark-Elves and wished to learn more of their magical secrets. The castle became his citadel for many years, during which time he grew into a malevolent undead spirit and trapped a powerful demon within the castle’s dungeons.

During the rise of the dark kingdom of Adar, the castle became an important eastern citadel of the Adari. After the destruction of Alokkair and the kingdom of Adar, the castle was abandoned for many years. It was then taken over by a rogue group of evil knights of the Order of the Süroth. The castle then became the capitol of their their new nation.

In the Fifth Age, when Sorimmar was banished from the Ravinian Empire and sent into into exile, he came to dwell at this castle and soon took control of the Süroth knights and their territory. With the rise of the realm of Morgoth and the capture of Erôn-Mystarë, Sorimmar left Erôn-Mored and dwelt at the newer and much larger castle of Erôn-Gothmar.

He then gave the island castle to his seven Zûl to be their citadel of fear and despair. The castle was besieged and burned down by the armies of the West at the conclusion of the War of the Cataclysm, but not completely destroyed. It currently remains a blackened and charred ruin, inhabited only by the Zûl and an army of orcs and undead creatures.