The Ring of Rage is an ancient magical, emerald-green object of the Ghost Zone, used by the Ghost King Pariah Dark. The skull ring that is, due to his its name said to give a wrathful, angry influence over whoever wears it and unleashes such rage and fury upon anything or anyone who stands in the way. If used while wearing the Crown of Fire, the user is given Unlimited/Infinite Power and Absolute Might.
The ring is completely green with a emerald-green skull with red eyes and a black background circle. The size changes depending on the user's hand.
He was beaten and overpowered by an mysterious ancient group of ghosts that stripped the two relics (both the ring and the crown) after the battle, and then they locked him up in the Sarcophagus of Forever Sleep, where he would rest for eternity.
Vlad Plasmius used the Skeleton Key he had stolen to get the ring and its infinite power. When he put it on, soon he realized he had to wear the Crown of Fire, which was locked in the sarcophagus, since Pariah was using it when it was locked. Vlad opened the sarcophagus and released Pariah, who easily defeated him and forced him to give him the ring, but Vlad escaped with it.
To avoid being attacked by Pariah, Vlad gave Valerie the ring. When the Fright Knight and Pariah Dark went to Amity Park looking for it, Valerie put it on a rocket that she fired, in an attempt to buy time to save Danny and Vlad. Pariah catches the missile and puts the ring on, getting infinite power after he at last obtained his 2 prized possessions.
During the final battle against Danny (who was using the Fenton Ecto-Skeleton that increased his powers 100 times but consumed his energy) Pariah fought in a fight fairly evenly matched, but the infinite powers of the king protected him from losing. Danny used what energy he had left to get the Crown of Fire and the Ring of Rage away from him, and lock him back in the sarcophagus.