Forsaken Fortress

The Forsaken Fortress is a fortress built at around 246 on a small island near the northeast coast of Lanayru, in the Necluda region. It used to be used as a watchpoint, defending Hyrule from invasor from the north. But eventually falling into despair and being overtaken by Malice.

History
The Forsaken Fortress was originally built in collaboration with the Sheikah. Under secret orders from the King of Hyrule, a hidden laboratory was built underneath the island.

The hidden facilities included multiple experimentation chambers, storage rooms, prison cells and torture chambers, along with a burial ground and a library. These experiments focused on using Malice to create an undead army by infusing recently deceased corpses with it. Those corpses were often taken secretively from jails, with cooperation from wardens.

Sometime after, a experiment would fail, leading to the creation of a giant pool of Malice in the center of the complex, from there, multiple monsters would emerge and overrun the laboratories. The fortress was then abandoned, with many test subjects, experiments and data still inside.

Experiments

 * Edge of Duality, a failed experiment to recreate the Master Sword. It is the second most powerful sword, after the sword of Evil's Bane. It is the only other sword capable of dispelling Malice, but is extremely fragile and will shatter after prolonged combat. Sheikah magic enables the sword to reform itself after some time.
 * ReDeads reanimated corpses with Malice. Created to serve as an undead army, but the experiment was stalled after they were shwoed to be incapable of following orders. They now guard secret places.