The Expanding Universe (Vol 4), edited by Craig Martelle, features Lights Out from the Bringer of Chaos series. The tale serves as a standalone story and introduces the character Six in his life as a ghost, back when he was known as Tornahdo.
Why that name? Ghosts were all special ops soldiers who had died and been resurrected. Their call signs often reflected some aspect of their fighting skill. For a Hispanic-Terran soldier with whirlwind fast reflexes, tornado–pronounced “tornahdo” in Spanish–fit.
Save Mankind: Lights Out
He can save mankind. After he does this one important thing. Die.
Join the Ghost Corps, they said. You’ll live forever, they said. You’ll save mankind, they said. They didn’t say that to do it, first he had to die.
When Tornahdo signs on the dotted line, he puts his life into the steady hands of the mighty Ghost Corps. Three grisly deaths and three agonizing resurrections later, he’s assigned duty on the space station Enderium Six.
He’s facing his most dangerous mission yet, the very reason the corps exists.
Tornahdo and a team of ghosts must take out the man responsible for every war between humans and Ultras since the origin of the Ultra bloodline: the immortal king, Pietas.
If they succeed, the war is over.
If they don’t, the Ultras will rule mankind for another thousand years.
Pietas regenerates from every wound. He’s so fast, no human has ever laid a hand on him. As a precaution, they’re sending in Tornahdo’s squad only after evacuating the station and trapping the king in a chamber emptied of air. The immortal will have to fight in a vacuum.
So will Tornahdo and his crew.
Do they expect the corps to win? Fat chance. Tornahdo and his team are already dead men and this mission is codenamed “Lights Out.” No, there’s more to this than Tornahdo can see.
To discover the truth, he must face an unbeatable, unkillable enemy, and this time–somehow–find a way to keep himself alive…
When you’re a ghost, it’s Lights Out. But it might be the only way to save mankind.
To learn how he ends up being called “Six” read Bringer of Chaos: Origin of Pietas. In the story timeline, that book immediately follows this story.