Future Dick Grayson
The man who the Team Titans knew as Dick Grayson (Nightwing) was really not Dick Grayson at all.
Deathwing's story began 10 years in the future; Or, rather, the false future where Lord Chaos reigned and a force known as the Team Titans struggled to overthrow his tyranny. Lord Chaos sought to destroy the rebels known as the Team Titans. This timeline's version of Nightwing served with the Team Titans as drill sergeant.
He was very much like the Dick Grayson of our timeline, but darker and a little more driven. In his time with the Team Titans, he took on Redwing as his protégé, a sort of Robin to his Batman. He also met Mirage, who fell in love with him. The two embarked on a relationship shortly after meeting.
Shortly thereafter, the Team Titans leader gave the team a mission: travel 10 years into the past to stop Chaos from ever being born. To accomplish this, the Teamers were assigned to kill Donna Troy before she would give birth to the child who would become Lord Chaos! The Teamers successfully traveled to the past and came into conflict with the Titans. Donna gave birth to her son before the Teamers could intervene. However, the Titans and the Team Titans were able to stop Chaos and spare Donna's life at the same time.
A Better : Deathwing Emerges
After this, the Teamers found themselves stranded in the past, unable to return to their future. With nowhere else to go, they resided at Donna Troy's farmhouse. The Teamers tried to find a place in this new world. Just after this, the alternate-future Nightwing traveled to our timeline. Mirage was reunited with her lover only briefly. A dark version of Raven attacked the future Nightwing and corrupted him by planting a Trigon-seed within him. Nightwing now renamed himself Deathwing, and became violent and brutal. Deathwing visited Mirage, where he attacked and raped her. Mirage then learned she was pregnant with Deathwing's child.
Shortly after this, the Teamers lives were disrupted by the time crisis known as Zero Hour. It was then revealed that the Team Titans leader in the future was the villainous Monarch - who created a false future world so he could train meta-humans (The Team Titans) to act as sleeper agent assassins. He knew of the impending time crisis, and wanted a super-powered army at his command. The time-villain Extant commanded all the Team Titans to attack the heroes who were trying to unravel this time crisis. His plan was thwarted; the heroes contained the Teamers. Time continued to collapse, erasing the false timelines that had emerged. As a result, all the Team Titans were erased from existence.
Strangely enough, three people remained unscathed from Monarch's false timeline: Tara Markov (Terra II), Mirage and Deathwing (who was believed to be a future Dick Grayson). Terra and Mirage remained members of a new Titans team, led by Arsenal. Shortly after the team was reformed, a strange orb appeared, with messages for Mirage and Terra.
The orb was sent by the Time Trapper. The Time Trapper revealed that Mirage, Deathwing and Terra were from this timeline, not an alternate timeline, as they had thought - which is why they survived the time crisis. Mirage was actually a runaway street urchin from where the Time Trapper kidnapped her and implanted false memories in her brain; she believed she grew up in Monarch's false timeline. The Trapper became aware of Extant's petty manipulations of time, and set up his own sleeper agents (Terra, Mirage and Deathwing) that would be able to fight Extant's programming. The Time Trapper also revealed that Terra was from this timeline as well. Deathwing's true identity was not revealed by the Time Trapper and remains a mystery.
Deathwing: Shaved Head and Leather Look
The Titans eventually came into conflict with Raven once again. Deathwing remained in Raven's thrall, and adopted a new look: shaved head, body paint and leather attire. During this conflict, Mirage was captured by Deathwing. Deathwing took a sadistic interest in his unborn child. At this time, Deathwing told Mirage that he is aware of his true identity: "Some guy in a robe sent this orb - it told me the truth! And trust me Miri, you don't want to know what I was before I became Deathwing!"
During the ensuing battle where the dark version of Raven was at last expunged, it appeared that Mirage had a miscarriage. Deathwing seemed genuinely upset at this news, in his own twisted way. He was rude with Mirage. He always treated her without respect, like she was his property. Till the end of Evil Raven he was loyal to her.
In truth, Mirage was still pregnant and used her illusion abilities to make it appear otherwise. She eventually went into labor while the Titans were off-world on another mission. She gave birth to a baby girl, who she named Julienne. Mirage then elected to spend time with her baby, and shortly after that, the Titans disbanded.
Deathwing is unaware his child survived. When he was last seen, he was at S.T.A.R. Labs under observation. It is unknown whether the Trigon seed has been expunged from his system.