Chaos Sphere

Additionally, an artifact known as the Chaos Sphere has at times been used, mainly in Hexen and Hexen II, as a source of extra power for the Serpent Riders.

The Sphere plays no active role in the battle against Korax in Hexen; however, in Hexen II, the player will encounter it after defeating the smaller and weaker form of Eidolon, causing the eldest Serpent Rider to grow to mass proportions. It has 2000 hit points here, and must be destroyed; otherwise, Eidolon will remain invulnerable to any attacks.