En Sentac

En Sentac was a veteran agent of the Division.

They were told about the imprisonment of Swarm at "the dawn of the universe", although they did not witness it personally and believed it may not have happened quite as early as the florid phrase made it sound. Over "millennia", it repeatedly fell to them to visit Swarm's containment chamber on the "remnants of the Burnished Rage battleground".

In 2021, shortly after they arrived with K-Toscs, Swarm took advantage of a shortage in the security facilities to use his powers to paralyse En Sentac and then drain their life force, causing En Sentac to disintegrate into ash and allowing Swarm to use the energy to renew himself into a healthier body. (TV: The Halloween Apocalypse)

Behind the scenes
No pronouns are used on-screen for En Sentac or K-Toscs, but the script for The Halloween Apocalypse used singular they for En Sentac and he/him pronouns for K-Toscs.