He, at some point after his town was "killed", joined band of elven disgruntled young and fell ever deeper into hedonism and depravity - hatred for humans - and all things not elven fueled by his recent loss and bad company. They pillaged, raided and killed for years. He never stopped to think about it, in his mind the carnage justified by what was done to his people.
Luckily for surrounding humans there were also orcs and goblins to raid and kill and even in hatred, elves were slow to move, having some pleasure in hunting of those who escaped.
He was finally snapped out of it in one raid where he witnessed (and stopped) killing of a woman with the child. While he saw the same thing done before, both of elven women and children during the raid that triggered the hatred and later done by his peers and even him (area spells are not really selective) - this one was final straw. He stopped the killing and ran out with the woman as his companions turned against him.
The feeling would pass and he probably could get back to them...but he couldn't. Not anymore. Simmering anger that would freely flare at the sight of human was still there and he didn't take care of the woman as he could. He never even learned her name. Arduniel left her and the child in the vicinity of human settlement, marked both of them with arcane mark and left her to live or die with humans.
By now, she is probably dead of old age and the child grown person.
He returned to the town, returned to his studies and advanced...but for the changed focus, from destruction to creation - he still contended with hurt wherever he saw scars from the raid. He tried exposure tactics and visited human monasteries where self-awareness was cultivated, but he still hated too much. He couldn't integrate fully with normal elven society, not after what he did and how he felt. Finally, he isolated himself with his book and spent a decade getting into the secret of runes and magic of life and death. He studied, built, learned with elven patience. And finally, one day, his metallic creation, sin rune of wrath moved, imbued with his own wrath. He felt drained, but finally at peace with himself.
He moved freely now, among elves, humans even dwarves - learning their ways, history and cultures. He was trying for peaceful solutions where possible. But he was also powerful arcanist, destruction incarnate when aroused.He lives in another shattered city, the one they are now, helping elves rebuild, more often themselves than the city itself.