Sword of Shadows

The Sword of Shadows was crafted to be the opposite of the Sword of Light. Originally it was turned from the Sword of Light to the Sword of Shadows, but when they were recrafted they were two different swords.

In Dragon Quest 11
The Sword of Shadows was the Sword of Light before Mordegon stole it and transformed it. After Mordegon's defeat, the Luminary took it and used it to make sure the World Tree was never destroyed by going back in time. The Sword of Shadows was destroyed in the process.

Creation by Xyle the First
Xyle the First created the Sword of Shadows (at the time called "Sword of Destruction") before he created the Sword of Light. The Sword of Shadows was created so that anybody could wield it, and it was obscenely powerful. Xyle then created the Sword of Light, which could only be used by a select few. He went through more trouble to seal away the Sword of Shadows because of its accessibility.

Use by Elyx
Elyx broke into the Temple of Stability and obtained the Sword of Shadows. Xyle got the Sword of Light at the same time. Elyx would use the Sword of Shadows as his weapon of choice until his defeat by his daughter, Lala.

Use by Lala
Lala used the Sword of Shadows as her weapon of choice, along with various magic spells. She can summon it to her whenever she needs it.