I think The Atumbra would be a fitting name for the new species. Umbra is the latin word for shadow, antumbra means before shadow and is used to describe when darkness is encircled in a ring of light such as an eclipse. I shortend it to Atumbra for naming purposes since I think "A" sound is more pleasent and catchy than the "An" in the original translation. It also thematically represents the faction since these are shadow beings encased in a universe of light. The individuals of the race can also be called Umbrials since they are the center shadow of this galactic empire, doesn't hurt it's an ok sounding name too if a bit cliche.

This is a really cool suggestion. It has a fitting etymology, but it's changed just a little to make it sound more alien. I'd be happy seeing this in-game. My one suggestion is that "Umbrials" doesn't sound quite right: it drops the first syllable and changes "-bra" to "-bria." Why not go with "Atumbrals" for individuals?

Umbra is just the latin word for darkness so it would make sense to derive the citizens of the empire itself from that word which Is why it starts at "umbr-". The reason for "-brials" as opposed to "-brals" is to make it sound more irregular without diverging too much from the faction's title. However saying it again I'm starting to prefer your suggested ending for the citizens.

Am I allowed to change what I call the citizens at this point to "Umbrals"?

Alright so frogsquad said the name change I made a week ago is ok, individuals of The Atumbra are now known as Umbrials. Voting is open too so I appreciate all the backing this gets.

*Not known as Umbrails. My bad.