Vecna is a great sorcerer that existed in roughly 15 B.B. He sought to become a god himself, though through means other than ascension. He is considered the very first Lich in Elion.
Before Attempting Ascension
Before attempting to ascend to godhood, Vecna was a great and powerful sorcerer that fell in love with Pandora, the first human. Vecna, considering himself a devoted servant to Nerull, used magic to kill many of his enemies, sending their souls to the God of Death. He also employed the assistance of many, building a respectable sized army to lay waste to the world in the name of Nerull. At his peak, Vecna had four generals (One being Kas The Betrayer.) and as little as 2500 soldiers at his disposal.
It wasn't until the intervention of the Gods that Vecna sought to ascend. During an event known as "The Battle of A Thousand Eyes", Vecna attempted to make himself the sole magic user by committing a magic-user genocide. It was at this point that the Gods, Pelor and Baccob, stepped in and stripped him of his magic, did the battle end.
Afterwards, Vecna, enraged at the Gods of their supposed betrayal, came to the conclusion that he would ascend to godhood, return his powers and exact revenge upon them.
In order for Vecna to ascend to godhood, he found that he required a piece of the Ever-Flame that exists in the godly realm of Arborea. Vecna used his beloved, Pandora, the only mortal being capable of entering the godly realm, to enter and steal it.
Pandora was caught by Nerull, and, as punishment, Nerull opened Pandora's soul (killing her in the process), allowing all the darkness that Vecna had poured into it, to seep out into the mortal realm, causing evil to exist in Elion forever more. Vecna was punished by the Gods for his continuous attempts at opposing them and tricked him by giving him what was thought to be the Ever-Flame. This turned out to be a ploy by Nerull that cursed Vecna into a hideous creature un-able to die. (Creating the first Lich)
Vecna's soul was placed in a phylactery, a container that housed his very essence and hidden in Elion, his body roamed Elion searching for his soul until its eventual decomposition. Due to his immortality, Vecna exists as essence in the hidden phylactery.
The Hand & The Eye
During "The Battle of a Thousand Eyes", Vecna was betrayed by his general Kas. Kas was bargained with by Nerull that should he kill Vecna before he commits the magic-user genocide, Kas will be endowed with a godly Boon. Kas, hungry for power, used the blade that was gifted to him by Vecna to attempt to take his life. However, Kas was only able to remove Vecna's right eye and left hand before being struck down.
These items, the Eye of Vecna and the Hand of Vecna, were also endowed with the curse of Nerull, however, due to being detached from Vecna's original body, they do not decay, allowing them to bestow magical properties on any foolish being that attempt to use them.
In order to use these items, the user must remove their own hand and eye and replace it with Vecna's giving them a small portion of Vecna's power.