Eris

Eris is one of the antagonists from The Grim Adventures of Billy and Mandy.

Destiny Hearts series
Eris appears as one of the major antagonists of the Destiny Hearts series. She also serves as the major antagonists throughout the overall of the series, unlike the Cartoon Network villains. Her origin begins in Destiny Hearts Birth by Sleep, in her home world, Endsville, she meets Naskenort. Their contact leaves Eris with the knowledge of the eight princesses of light, thus beginning her journey to gather all the princesses and unleash chaos upon the worlds, claiming them as her own, leading into the events of Destiny Hearts. In order to achieve her goal, Eris enlists the assistance of other Cartoon Network villains: Sylvester, Aku, High Roller, Vilgax, Boogeyman, and Father. Together they bring chaos to their worlds and collect the princesses of heart through control of the mysterious creatures known as the Discords. However, one boy stands in their way, that boy being Muto, the Keyblade's chosen one. With the help of Porky Pig and Daffy Duck, Muto manages to travel across the worlds, defeating each villain, and eventually finding himself in Hollow Bastion, where Eris has built her home base. A battle follows, and eventually, Eris is killed.

In Destiny Hearts II, she revives from her death, the only villain still in contact with her being Sylvester. Together, they continue their quest for power, by merely invading worlds and attacking with Discords, but a new threat is known as the Organization XIV gets in the way of Eris's quest for power. Eris and Sylvester appear to sacrifice themselves in order to hold off a horde of Discords so that Muto, Maku, and their allies can defeat Organization XIV's leader, Xemnas.

Eris also appears in Destiny Hearts: Chain of Memories, Destiny Hearts: coded, and Destiny Hearts: Dream Drop Distance, where she appears as a considerably minor character, looking to consolidate power and antagonize both Muto and King Bugs Bunny.

She returns as one of the main antagonist of Destiny Hearts III.