Sontaran-Prime

In an alternate timeline where the Cybermen used Time Lord resources to conquer all of history, the Sontaran-Prime was a first-generation Sontaran, and the leader of the Last Great Sontaran War Fleet in the 24th century following the Sontaran Empire's near-complete destruction by the Cybermen. (COMIC: Supremacy of the Cybermen)

History
In the 24th century of an alternate timeline, the Sontaran-Prime ordered a squad of Sontarans, led by Commander Sturg, to capture the Tenth Doctor for his assistance in the Sontarans' war with the Cybermen, who had destroyed nearly the entire Sontaran Empire in a campaign to eradicate any species that would constitute a serious threat to the Cyber-Empire.

Following the capture of the Doctor, Gabby Gonzalez and Cindy Wu at the Cosmomart, along with the crash-landing of the Imperial Flagship on Sontar due to an attack from the Cybermen, the Sontaran-Prime explained to the Doctor the reason for his capture, and ranked him as field marshal of the Last Great Sontaran War Fleet. When the Cybermen began attacking Sontar via Gallifreyan portal technology, a Cyberman exited a portal behind the Doctor and attempted to kill the Time Lord; the Sontaran-Prime shielded him from the Cyberman's blast, and was killed. In a state of shock, the Doctor briefly mourned the Sontaran-Prime before Sturg killed the Cyberman and informed the Doctor of the approaching CyberKings.

At the end of the universe, when the Twelfth Doctor and a betrayed Rassilon used the Eye of Harmony on Gallifrey to regenerate the universe, the Sontaran-Prime's encounter with the Tenth Doctor was erased from history, as were the rest of the alternate timeline's events. (COMIC: Supremacy of the Cybermen)

Appearance
Unlike traditional Sontarans, the Sontaran-Prime had a long, grey beard and moustache. The Prime additionally lacked a right leg, with what appeared to be an artificial replacement for his left leg. The Sontaran-Prime also wore large grey armour, with blue epaulettes featuring numerous light blue swirls. He also constantly sat on a large, blue throne with various controls that hovered above the ground, and was also highly mobile, as evidenced by how quickly the Prime was able to manoeuvre himself to shield the Tenth Doctor from a Cyberman. Unlike most Sontarans, the Sontaran-Prime had red blood. (COMIC: Supremacy of the Cybermen)

Personality
Like most Sontarans, the Sontaran-Prime glorified war, marvelling at the sight of Sontarans marching into battle against the Cybermen. The Prime even commended the Cybermen for their conquests, noting that the Sontarans had never seen such ruthlessness, and considered it "glorious", much to the chagrin of the Tenth Doctor. However, the Sontaran-Prime also appeared to mourn the devastation caused by the Cybermen, in particular the destruction of the Sontaran Empire save Sontar itself, Alpha Centauri and even the extinction of the Rutans. The Sontaran-Prime also held the Tenth Doctor in high regard, referring to him as the "Champion of Time" and noting that the Time Lord had witnessed warfare unlike anyone else in the universe. The Prime's respect for the Doctor was such that he declared the Doctor field marshal of the Sontarans in their final battle with the Cybermen, and even sacrificed himself to save the Doctor from a Cyberman. (COMIC: Supremacy of the Cybermen)