The Chaos Crescent is a powerful Shade artifact. It is also one of the oldest on record.
Originally, the Chaos Crescent belonged to Marrow the Unnatural, who wanted to take over the Royal Shade Throne. After being defeated, Marrow lost his Chaos Crescent and was forced to retreat to his place of origin. The Chaos Crescent apparently can shift the balance of chaos in an area, and can cause a lot of calamities to occur in that area; such as earthquakes and tornadoes. It is the most dangerous artifact that the human race has uncovered since it's inception on Earth.