Tyrael was a Nephilim who lived during the days of The First Void Insurrection, and was the elder sister of Cyratel. She is among the few of the Nephilim to ever unlock Dual Personas. She lived mostly in the shadow of her younger brother, who was treated as a deity. Safe to say it did not affect her too deeply. Some say she chose to be oblivious to Cyratel's rise in power, and the effects Void had on him.
Though struck deep by the truth of the matters, she had no choice but to assist the rest of her kin combat the Void Avatar once the Insurrection truly broke out. More notably, she helped bring down the corrupted Collosi known as Void Collosi, and she contributed in the efforts made to keep the Void Infectation contained. This she considered her main goal in the Insurrection, favouring Lord Knight Falken to bring down her lost brother.
During the aftermath of the First Void Insurrection, known as the Nephilim Purge, she was hunted down. As her kin was slaughtered around her left and right, she tried to continue her task by tracking down the remnants of the Void Collosi. After being cornered in Hell, she was confronted by the Demon King, Samael. The two fought a gruesome battle, but ultimately Tyrael stood victorious over Samael. Instead of putting Samael to the sword, she locked him away in a Void Prison in the deepest reaches of Hell, for reasons unknown to the Demon King.
Being mortally wounded herself, she spent the remainder of her life in Eden, where she eventually died. Her final resting place is still a mystery to this day. Scholars to this day are still baffled by her choice for Eden, and their attempts to discover her resting place have been futile, least to say. It is widely speculated she fulfilled somekind of final service to the Worlds on Eden, but nothing has been confirmed on the theory.
Tyrael was considered amongst her own kind to be one of the most powerful to walk the Worlds. Both a veteran practitioner of Soulcraft as well as a highly refined swordsman, she was deadly enough to easily flay a Void Collosus with a few precise strikes while keeping the Void within it supressed and contained.
Tyrael was the last of the Nephilim able to invoke two Personas. Her two Personas were known as Alphus and Omegus. Alphus was the dominant Persona, having incredible power with Soulcraft, while Omegus personified her ability to use Void.