Widdershin is the main antagonist of Tales of the World: Radiant Mythology, the only Tales of the World videogame to be released in both North America and Europe.

He is a Descender like the protagonist and Mormo which means he was born to defend his world. After his world, Gilgulim ran out of mana, he converted it all into a world seed and sought to create a single eternal being from it by having Gilgulim absorb the mana from other worlds. After he had Gilgulim absorb Yaoon, Mormo's home, Widdershin set his sights on Terresia. However, it was difficult as Terresia's World Tree had an extremely large amount of mana, giving his ally, Kanono, the Descender of a world known as Pascal, amnesia.

Mormo reached Terresia's World Tree and told it of the danger Terresia would face. It then gives birth to its Descender, the protagonist of the game.

By this time, Terresia inhabitants had begun calling Gilgulim the Devourer. It is only after defeating Ganser that Widdershin reveals himself and Gilgulim's name. Despite destroying several nodes and even destroying Aurora, another Descender and second-in-command to Widdershin, and her mana lab, Terresia's World Tree started to die, allowing Gilgulim to appear to begin its harvest. Kanono, having been an ally since her amnesia, uses her power to temporarily stall the mana harvest.

The protagonist enters Gilgulim and finally battles Widdershin and defeats him. With his destruction, Terresia's World Tree absorbs Gilgulim's mana and sprouts seeds, helping to rebirth all the worlds Gilgulim absorbed, including Pascal and Yaoon. Gilgulim itself is rebirthed as well. With Terresia now safe, the Terresian Descender goes deep into sleep.

Widdershin was incapable of emotion and did not understand why people did not want to be part of a single eternal being and believed what he was doing was good.