Overlord Mandark is one of Mandark's Future Selves from "Ego Trip". He is Mandark's tyrannical middle-aged self and the ruler of the world. He is a merciless and evil despot who rules the world with fear and an iron fist and prohibits the use of technology to all.
In his past, Overlord Mandark was Executive Mandark, the head of The Corporation who treated his employees like slaves and loved to torment his most hated former adversary Number 12 aka Dexter's adult self. One day, the Dexter from the past appeared to restore Number 12's confidence and took him to the future to meet Old Man Dexter to find out how they saved the future. However, Number 12 had accidentally left his Neurotomic Protocore exposed, allowing Executive Mandark to finally steal his most long sought after goal from Dexter. He then tried to harness the power of the Protocore but set its positive flow to negative. The now corrupted energies of the core began to twist Mandark's already crooked mind, making him more greedy and insane than ever before. The negative energies emitted by the Protocore numbed the minds of the planet's populace, allowing him to easily take control of all the world's technology, knowledge and societies, thus becoming the absolute evil ruler of the world. With his new found power and luxuries, Mandark spent the majority of his time lounging in hot tubs and became quite obese over time and needed a grappling hook just to move about. Most of his actions involved trying to thwart Action Dexter's attempts to help the populace.
When the time traveling Dexters prepared to battle Overlord Mandark, he immediately sent his robots to destroy them but when that failed and they arrived at his fortress, Overlord Mandark summoned his own past selves to help him, including Mandark, Executive Mandark and Braindark. During the fight, Overlord Mandark and Action Dexter had an epic clash and exchanged numerous and painful heavy blows. Eventually Action Dexter was able to gain the upper hand by loosening Overlord Mandark's grappling hook, causing him to fall flat on his face. When the Dexters prepared to deactivate the Neurotomic Protocore, each of them were grabbed by their respective Mandark (the Overlord doing so with the aid of his bulldozer), but before they could deactivate it, Dee Dee appeared from Dexter's Time Machine and all the Mandark's immediately fell in love after seeing their beloved Dee Dee after so long. Dee Dee then unknowingly de-activated the Protocore and set its energy output to positive, which undid all of Overlord Mandark's evil and caused his body to explode, leaving behind only his brain and thus turning him into Braindark. Mandark, Executive Mandark and Future Braindark where then sent back to their own time periods. Braindark's disembodied brain was then placed in a confined jar with a communicator by Action Dexter where he would spend the rest of his days as punishment for his evil crimes.