Vasculio

History
Vasculio was originally an apprentice of Erstam.

When he was in Moonshade, Vasculio specialised in Death Magic (not like Mortegro who speaks to the dead. Vasculio was interested in causing death--quickly or otherwise. He tortured and killed, using the ‘death agony’ as well as Stoneheart to fuel his spells). Tipped off by Mortegro, the Council of Mages went to speak with him and caught him in acts so horrible it was determined he was no longer human, so Filbercio sentenced him to death. Not a week after the execution, Vasculio's tomb was found open and empty. Ensorcio, who was Vasculio's apprentice, says Vasculio had been working with stoneheart, and his experiments enabled him to escape death (Vasculio once stumbled upon a magic formula which, when used with the blood of an innocent, allowed a dead body to live longer. Moments before his execution he used this spell).

Note that Torrissio was working with Vasculio but managed to weasel out of justice while leaving Vasculio to his fate.

Vasculio went to the Skullcrusher Mountains because he knew there was a second source of stoneheart there, and he knew the Moonshade mages would never follow him into the Icelands.

Vasculio did not seem to have fully escaped death. His own records show that he used spells and Blood Spawn to keep his body animated, and needed to drink blood out of the living to keep himself ‘alive’ (suggesting that hs is actually a vampire).

In Serpent Isle
When the Avatar meets Vasculio, he's 'sleeping' inside a coffin located in the remains of an Ophidian city beneath Skullcrusher. Vasculio says he will let the Avatar live in exchange for one of the lives of his/her companions, but whatever descision is made, combat is inevitable.

Vasculio keeps many interesting (but not always useful) items in his abode, and the Avatar's Spellbook can be found in his workshop (though at this point in the game, the Spellbook is worthless as it likely has fewer spells than the replacement the Avatar got in Moonshade).