Myrwhydden is a sorcerer and an old enemy of Abin Sur.
Many years ago, Myrwhydden enslaved the minds of a community of people, until Abin Sur freed them of his mind control. Myrwhydden was reduced to microscopic size by the Green Lantern, and sent to a pocket dimension, with no chance of escape.
Over time, Myrwhydden attempted to boost his power signal from a nearby crystal to create a portal to free himself from his prison, which succeeded until Hal Jordan's ring was near it, Hal and Razer fell through the portal, trapping themselves in the pocket dimesion. Myrwhydden introduced himself to the duo, and insisted that Hal create another portal. Afterwards, Myrwhydden discovered Abin Sur's ring was in Hal's possession and transformed Razer into a mutant velociraptor. Myrwhydden raced to the portal, but Hal interfered his escape.
However Myrwhydden still managed to escape the pocket dimension by channeling his essence into the power beam from Hal Jordan's ring. Myrwhydden eventually was defeated by Hal, Kilowog, and Razer when they channeled Myrwhydden's path in the beams of the Power Rings by crossing the path of their beams, reducing him to particles and scattering his essence and absorbed in the Power Rings of the three Lanterns. Which his only escape could be if the three beams cross each other's path again.