Rabia was sure Sombra would bring prosperity to the Umbrums. Her son is powerful, in a pony form he could easily get through the Crystal Heart's magic and destroy it, open the door and free them. And than the eternal hatred and fear will fall upon the Crystal Empire. And soon to the entirety of Equestria.
But in the end he wasn't. He was weak. Not his magic, his heart and mind were. Falling for the ponies' love and betraying his kind. His own mother. Locking them away again without a second thought. He could have been the king of all, but he rather choose to be a nobody.

Rabia's anger knew no bound. For his own son. For the ponies who poisoned his mind. She still didn't give up. The Umbrum will be free one day. But how? Rabia lost connection to Sombra's mind, there no other way to look outside the door.
Than years later, something that weren't even a year for the umbrums, a faint presence were felt by her. Something outside the door. It felt like an umbrum but different. Sombra? No, it can't be, it's weaker than Sombra was. Not just weaker, it was really weak, she knew breaking through this mind will be easy.

Without any effort, she stood in front of the host. And it was just a small, frightened little filly. Rabia knew in a second what was going on. This pony was Sombra's daughter. She looked like an ordinary pony, but there was no doubt about it. Deep down in her soul she was part Umbrum.
Which couldn't make Rabia happier. Just a small pony, but one day, she may help the Umbrum rise again. She will make her, by all means necessary. She will have her revenge. Ponies took her son, now she will took something from them. However, for that to happen, Rabia needs to make the first step.

"Finally I met you, my grandchild."

—-

Wasn't sure if the next AU stuff should be me more thing with Sombra and Noche, but might aswell. I wanted to do more with the Umbrum for a while now, together with Rabia. Even tho drawing her was both fun and a bit of a task to do. In the end hopefully, I managed to capture that creepy, skeletal/ghostly look of an umbrum.

Extra info:

1. I don't think it was stated in the comic, wether or not Rabia was Sombras mother. For me it made a lot of sense, because why would the leader of the Umbrums allow just a random Umbrum to become the king after their escape, if it wasn't for familiar ties. Well, at least for me, so that's my headcanon.

2. Rabia appeared in Noche's 'dreams' but not all the time. Despite the title of the drawing, they weren't actual nightmares (not even dreams, really) , so Princess Luna couldn't protect the young filly from Rabia's influence and torment.

3. In the Umbrum real time passes differently, for example that's why Radiant Hope didn't age when she was spirited away.

4. In the comic (the Sombra issue of FIENDship is Magic) we see that Rabia used a red crystal to communicate with Sombra. In the AU, the crystal was just a remnant of the Umbrums' magic, and it just helped Rabia's telepathic communication with Sombra. As the Crystal Heart cut of the communication between the two (something Rabia did not expect).

I think that's all the extra info needed. Everything else will be talk about in future drawings.

Fun fact, originally I wanted to name this drawing 'My Sleep Paralysis Demon', but it didn't made really much sense. It just sounded cool to me.XD