Dimentio

Lord Timothy Johnson Harvey-Dimentio (known only by his adoptive family name) is the Master of Dimentions, Arch-Villainous Jester, Pleaser of Crowds, Dark Alchemist of Paradox and Angela O'Haru's evil twin brother separated since birth and raised by the royal Dimentio Family, but then after finding out the truce that he wasn't a no-face but a Human boy that wears a mask, Poor Tim lost his sanity. Now running away from the No-Face Kingdom and teleporting to the Mario Universe, heading towards the Village full of the Tribe of Darkness, joining in to become the Dark Alchemist like the other tribesmen of Darkness who turn against the ancient Shamans in the Tribe of Ancients. But after finding out that Lord Blumiere was heart broken due to his father sentencing Timpany to travel around dimensions until her game ends. he turns to Blumiere's Split Personality, Count Bleck. He let Bleck take the Dark Prognosticus Book,

then Count Bleck and Dimentio ran out of the village by teleporting before leaving the Nuclear time Bob-omb to nuke the whole village, killing Blumiere's old man inside. Before the ending of the event in Super Paper Mario Ended, there was a final battle between  his super form, the Chaos Heart (which he had Bleck do by forcing Peach and Bowser into Marriage), Mr. L,, himself and three of the heroes of Prophecy After betraying Count Bleck. After Dimentio was defeated thanks to the Pure Hearts used by Peach, Bowser and Mario. He said "NOOOOO!!! I'll be back!!" and he went back to the Shadow Queen's Palace of Shadow.

Super Princess Peach: Ally or Enemy?
His Current Mistress, the Demonic soul of Lady Olivia, the Daughter of the Original Shadow Queen and current leader of the Tribe of Darkness, scolded one of her minions Dimentio for the failure back in the "Chaos Heart" Event but after that she blamed Vivian for helping Mario kill her mother. And as Punishment for the betayal of the Shadow Sirens, after Beldum, Cackletta, Midbus, Fawful, Dark Star/Bowser (resurrected by Cackletta) and Marylin brought in the dead corpse of Queen Melody Toadstool (Peach's Mother) for Olivia to possess, Dimentio saw that she turned Vivian  from a Shadow Demon into a Harry Hedgehog and banished her from the order of the Tribe of Darkness (which the Shadow Sirens are part of). He first met his twin sister Angela and they never got along at all. After you defeat Ultimate Dimentio (His ultimate form after using his Star Diamond, Mr. L. and Dr. T (the brainwashed Tails Prower, NOT the Hammer Bro) whether using Peach or Angela to defeat him) you can recieve the Star Diamond but he will not be playable in the game.