from the ingame lore:
'Listen well, Research Assistant Pharaxes Sphaerideion, for I will tell you a tale of misery and sorrow. A tale of the terrible evil that is at the heart of the Withered Aegis. A tale to freeze your bones and wither your spirit. This is not for the faint of heart! Leave now if ye have not the stomach.'

'Many years ago, there was a revered member of the Paladin Order by the name of Valkor. He distinguished himself during the early years of The Lament as the Withered Aegis and their Undead Hordes poured into Western Aradoth. So it was with great surprise when the Leaders of his Order learned of his disappearance. Or rather, his capture.'

'It was as they had feared. The Withered Aegis had ambushed Valkor and his wife while they were traveling to the small town of Harro from Feladan. They were taken, as the story goes, far to the east into the depths of Torrin Macalir's fortress on the Eastern Continent. There, Valkor and his wife were tortured mercilessly. Eventually, Valkor's wife succumbed to her torture and died.'

'Valkor, upon seeing his beloved wife's death, vowed eternal vengeance upon Torrin and the rest of the Withered Aegis. But he was still firmly imprisoned and continued to suffer gruesome torture daily. Despite Torrin's best efforts, Valkor remained strong and refused to give in.'

'Finally, after a year and more of unending torture, Torrin switched tactics. Break him with magic, he decided. And so he set upon Valkor with powerful necromantic magics... These magics warped and twisted Valkor's body, nearly destroying him, and turning him into a specter of death with a terrible thirst for the life force of others. The magics, though, had an even greater impact upon Valkor, one that physical torture could never have achieved... it broke his mind!'

'Valkor went mad beneath the evil magics plied to him. His hatred of the Withered Aegis for his wife's death and anger at the gods for abandoning them both to this fate, turned to unending rage, the source of a terrible, twisted power.'

'Torrin soon discovered that further tortures could no longer touch Valkor, so he simply locked him away, for decades, in a cell deep in his dungeons. Years passed. Rachival fell. Feladan fell. The Battle of Tazoon was fought. Torrin Macalir was destroyed, and the tide turned. Feladan was recaptured by the Gifted. It was at this point, with the power of the Withered Aegis waning upon the Prime, that Valkor finally escaped his captors!'

'Breaking free of his cell, he cut a swath of destruction through the Aegis minions who had remained behind to guard him. Leaving the fortress with a trail of pursuers, he ran aimlessly through the destroyed lands, obliterating all he encountered in his mindless rage, until becoming cornered in a portal complex. With scarcely a thought, he leapt through an open portal following a regiment of Aegis troops, returning to the unblighted lands of Istaria in the west.'

'In Istaria, he found that his tortures had turned him into a terrible creature, one that would be hunted in these lands. He found a ruined fortress high upon a mountain-top in the northern regions of Istaria and there, with an army of undead minions he found he was now able to command, he had locked himself away, his hatred festering for all these long years. His rage has given him power, but twisted his form. Valkor's form is the visage of death and his power can warp the world around him, as well as bend the beasts of darkness to his will.'

'He remains to this day, Pharaxes! Brooding, biding his time high atop the mountains in his fortress. One day he may come down and feast on us all! And that is the end of the tale...'
(worth to be put on his wiki page, isn't it? *ponders*)

Actually... I don't see, why he should feast on us all (except the countless battles for his weapon parts) because he still hates the Withered Aegis, not the Living Races.

So is he really considered to be evil? All he wants is to revenge the death of is beloved wife.