The Gnome King is a villain from The Wizard of Oz books by L. Frank Baum. He is the main antagonist in Tom and Jerry: Back to Oz.
Role in the film
When Scarecrow, Tin Man, and Lion surprised Dorothy, Tom, and Jerry by showing up in Kansas, they told her what happened right after she left Oz. Ruggedo, the Gnome King, returned to Oz and wanted to destroy Dorothy because she had the ruby slippers, and he scoured Oz for every magicl object he could get his hands on. According to Tin Man, only Ruggedo's great fear of the Wizard of Oz kept him underground. When Dorothy gave up her ruby slippers, Ruggedo turned them into boots. Dorothy did her best to stop the Gnome King and got the Jitterbug to keep him dancing until he was about to fall into the Pit of Gnome Return. Tom and Jerry caught him but wound up pulling off the ruby boots/slippers, and Ruggedo fell down the pit.