He was punished for stealing too much of Tempè's mana, as Cridhe was known to be an almost mana-less plane. Another part of his punishment was snake-tattoos on his arms which would come alive and kill him if he thought about or touched Tempè's mana.
He traveled this plane to finally appear on its mainland where he found an enormous source of mana hidden even from a planeswalker's eyes: the Clan Tree of Cridhe.
Malvos planned to find an suitable person, show him how to do magic, and then give him all mana from the Clan Tree of Cridhe so that one would become a planeswalker and they both could escape. Malvos wanted to travel to Ilcae, where he could find other planeswalkers like Platon or Krim. In exchange for information on Tempe's mana lines they would undoubtedly set him free from the snakes-tattoo curse.
His plan was simple but needed time. Eventually he a suitable person: he found out that Nohr was able to do magic and caused a stir between him and other people of his clan. Malvos made him drunk and gave instructions of how to use a magical sword he had stolen from Tempè to become planeswalker and leave the hated place. Unfortunately for Malvos, something went wrong. Magical rays from the sword missed the mana line and the Clan Tree was completely destroyed.
In this way Malvos brought an age of darkness upon the plane which would last for 520 years.
He was eventually forced to abandon his obsession with escaping his imprisonment on the plane of Cridhe, destroying the one artifact in his possession capable of transporting him back into the planes in order to save his life. Not much later, after the Mending of the Clan Tree he was devoured by a shroud in the form of a tent.