Salamander

Two hundred years ago, just before the Oblivion Crisis, a Khajiit boy named Eventide and his Breton girlfriend Babette were bitten by vampires, becoming vampires themselves. He joined the Dark Brotherhood, an assassin's guild consisting of vampires. While he was largely uninvolved during the Oblivion Crisis, it was during the Dragon Crisis when his life would take another turn. After the Dragonborn, Blackfang, brought down the Dark Brotherhood for good, Eventide would go into hiding, plotting his revenge. He founded the Neo Dark Brotherhood, changed his name to Salamander, and sought to kill Blackfang, becoming the new king of Skyrim in the process. However, his plans were foiled thanks to the interference of Blackfang's son, Dusk. Since then, Salamander has become rivals with Dusk, even going so far as to invade a fallen timeline of Kivotos, replace that timeline's sensei, becoming Phernapates. This vampire boy is still going strong to this day, challenging Dusk from time to time.

Calmer, colder, and more serious, Salamander could be considered the Shadow to Dusk's Sonic. While he can't use Dragon Arts due to him not being a Dragonborn, his fighting skills developed over two hundred years and his incredible power as a vampire allows him to stand on equal grounds with Dusk. Even his weapons are similar, being an M1911 and a two-handed falchion. Whereas Dusk practices shotokan karate, Salamander uses kyokushin. Only someone like Salamander could stand as Dusk's equal.