As to I am, you will know that when the sun sets forever!
~ Sev

Sev is one of the main antagonist of Rise of the Spartans and was the original Captain of Midsummer Night from Rise of the Spartans but was betrayed by his second in command, Lucas Gradeur. Due to being blinded and burned by the explosion of a plasma grenade, Sev was forced to amputate his own arm and replace it with a prostetic. He combined himself with the technology of a UNSC combat droid in order to fix his vision. He also scavenged and created his helmet by using aparts of a Gungnir and Security Helmet, and took armour from other dead bodies of marines. Sev also put halo energy into his Focus Rifle in a Forerunner facility, making it more powerful than regular Focus Rifles.

Sev wanted to get his own version of justice, so he led Archangel into a death trap and killed him. Swift discovered this and wanted to avenge Captain Archangel by killing Sev. 

Sev led forces with his accomplice, Sahjook, and engaged the forces of Commander Ryan. After eliminating three of Ryan's scorpion tanks and many of his men, he was engaged by Ryan himself and Whisper. After being overpowered, Sev retreated with his Wraith and escaped back to Shipmaster Ragath's base of operations. Ragath manipulates Sev into an alliance by informing him that he planned to reinstate him as the rightful Captain of Midsummer Night and that he had dispatched a team to repair the ship. He informs him that the human forces learned of his plans and destroyed the ship when in reality Ragath had used the ship as bait and had it destroyed in an effort to kill any Spartans or Marines that tried to reclaim it as their own. Sev states that he won't join Ragath but will fight alongside him and leads a large force to eliminate all remaining marine outposts and resistance.

Swift vs Sev
Later Sev is founded by both Whisper and Brass after he claims possession of the index and a colossal fight broke out. After incapaciting Whisper temporarily, he kills Brass who stays behind to hold off Sev and the elite forces so Whisper and the other marines could escape the facility. Sev later leads the forces in an attack on The Argonauts and their group of marines. He kills ODST Major Donnely and many other marines before entering the facility which leads to the control room. Nightflash and Sev arrive and engage in battle with Sev and Sahjook. After incapaciting Swift, Sev teams up with Sahjook and battles with Nightflash who forces Sev to his knees and kills Sahjook.

Ragath enters and mocks Sev's inability to deal with the Spartan's offering to deal with them personally but soon has to battle with both Ocelot and Raptor. Swift recovers and joins Nightflash as Sev approaches ready to continue their battle. Sev holds his own against both Spartans in close and ranged combat and as he continues to fight Nightflash he is unwittingly forced back into a large blue beam, ultimately killing him.

Later, Ragath plans on activating Halo and says he needs a human to activate them. Swift says his not going to be forced to activate them, but Ragath says his not going to use him. Sev then walks into the room alive and activates Halo, then says Ragath needs to do his part in their deal. Ragath then assassinates Sev, betraying and killing him.

Although Swift uses Halo to revive everybody who died on Halo including both Ragath and Sev. Ragath runs into the room furious at Swift and wants to take revenge, but one of Ragath's Honor Guard Elites is seen being shot and killed by Sev's focus rifle. Sev then continues to take his revenge and kills Ragath with his focus rifle. Ooskoo see's Ragath's dead body and asks who killed him, both Sev and Swift kept quiet believing he'll be furious, but Ooskoo thanks whoever killed him.

Sev is last seen with Archangel aboard the Covenant Ship where Firelight is imprisoned by the Elites.