A reward for bounty-hunting mission, Toxic Avengers.
Medusa Ray is a glove lance hardlocked to acid. That makes it a counterpart of Feuerfaust and Emperor's Touch, but sadly it does not stack well to either of them. Acid ray it makes is for some inexplicable reason much harder to aim then fire ray of Feuerfaust and lacks the self-guiding nature of electrical arcs from Emperor`s Touch.
Damage radius is biggest out of all lances, but utilizing it properly is finicky and special effect is rather lackluster.