I've toyed with a couple ideas, but none of them approached the concept of a Warforged necromancer. As a note, I don't have Races of Eberron, though I did read the Dragonshards article. If anything's severely amiss, feel free to point it out:
Agarndas
Biography: Agarndas, formerly known as F-92, emerged from the bowels of House Cannith five years ago, during the latter part of the Last War. He was assigned to a unit, called the Forgekeepers, with the responsibility of magically maintaining and repairing Warforged Titans. Rarely exposed to people of flesh and blood, his experince during the war was one of constant contact with fellow Warforged, from fellow Forgekeepers, who he quickly bonded with, to frontline commanders and warriors. His only contact with humans and other organic races was during occasional inspections from politicans and commanders. By the end of the Last War, the only beings he identified with were fellow creatures of metal and wood. All the same, he was thrust out of the employ of House Cannith and into Sharn, and a new world.
While the first days following his dismissal were disorienting and frightening, he quickly began to learn about the world of humanoids. He observed them with interest, noting their weaknesses: their fragile bodies that wither and die of age, their conflicts within their own races and groups, and their inexplicable hatred for things and ideas of their own making-such as himself. Their distaste for reminders of the war, such as his fellow Warforged, served no practical purpose, especially when considering that blame for the war rests squarely on their shoulders, not his.
The Warforged began making a study of humanoids and, in particular, their relation to the magic he had formerly worked to repair Titans. While most of his work involved observing humans-he favored making trips into criminal-infested parts of Sharn-he also began studying their bodies. While he found it odd that, after so many years of killing each other by the thousands, the city frowned so heavily on the death of a single man or woman, he avoided trouble by searching sewers and allys for corpses. In doing so, he encountered numerous interesting persons, living and dead, including another wizard (though not of mechanical origin) who found him examining a body. The man, a necromancer, taught the Warforged basic spells relating to life and death in organic beings. While Agarndas was no closer to understanding humans after the experince, he found his newfound magic interesting nonetheless. The necromancer gave him a second, equally important gift-his name, Agarndas, meaning 'Flesh-forge' in Quori. The Warforged adopted this name for himself in place of his old designation.
The warforged managed to perform his research undisturbed in the lowest parts of the City of Towers until he was found one night by the city guard while magically blasting a dead body, formerly owned by a member of the guard. He was hauled off to prison-a source of puzzlement to him, as it was plainly obvious that the man was already quite dead, and therefore no longer in need of his body-and spent several weeks there before he was scheduled to be transported to a more secure location. In a freak lightning rail accident, though, the ligher-than-normal carriage lost control and crashed only a few miles outside the city. Agarndas escaped unharmed, retrieved his possessions from an injured sentry, and ran away. He eventually found a small town, where he stayed in hiding and continued his observations of humanity. Several weeks later, he heard a summons from the east. Since his supply of interesting persons in the town was running thin and he suspected that the guard in Sharn would sooner or later track him down, he decided to heed the call.
Appearance: Agarndas has an average body for a warforged. Due to his status as a support unit, his composite plating is of ordinary steel and wood. His body still is covered (mostly) in white paint, an indication of his support role, but it has begun to wear off after countless days scouring the sewers of Sharn for bodies. He stands slightly shorter than most of his fellows, and has eyes that glow an unusually dark shade. He carries a sack containing his material wealth-his spellbook, a few relics of the war, and some coin.
