One (Idle Apocalypse)

Sid's personal hate mail delivery service. Ends up visiting his sister a lot, who is Very mad that he got to space first, mind you. One ends up in the middle of the sibling rivalry as they get closer to Enid.

Relationships

Enid—They're dating! She's obsessed with them & kinda hates it. How dare anyone associated with her horrible brother win her over like that.
Sid—He's technically One's boss, but they're mostly just doing whatever they want while Sid tries to steer them away from anything that would screw him over. Including Enid. He acts like an overprotective brother sometimes, but he just hates her and wants to sabotage her love life.

One (Necromerger)

A time travelling alien, at first just content to observe the flow of time. After discovering the Necromerger's ripples across spacetime, they become... particularly attached to Enid, and decide to interfere for once in their life.

Relationships

Enid—They're dating! One's seen her future and wants to save her from it.
Sid—He doesn't know they exist until Enid raids his armory for the first time after he travels back in time. He's honestly a little insulted that she's also enlsited alien help, but he doesn't realize that One and Enid have been time travelling along with him.
Other aliens—One probably isn't supposed to be using time travel the way they have been. They're laying low in the greater spacetime community right now.