(I don't even know what's going on with this title, really.)

(The explanation of these two takes place of my friend and I's canon. It's not the straight canon of the show or comics.)

These two are Erebus and Amani. Erebus is the Prince of Tartarus, who was shunned from the world in the light (A.k.a Equestria and such), and decided to train under his father Hades who is the current ruler of Tartarus. He's been shown very little kindness, and he's grown as cold as the world's perspective of him.
Amani is the daughter of Sombra and a currently unknown foreign Alicorn. She served as a general for Sombra's army, but when he was overthrown, she had no choice but to join Celestia and Luna and assist them with her alicorn magic. When Sombra attempted to return by taking over the Crystal Empire, Amani helped him against the others of the princesses, resulting in her banishment to Tartarus. This is how she met Erebus, and in her thirst for vengeance she sought his assistance. They became friends, and then even more than that.

Thus, my excuse to make a piece about evil love. Muahaha. twiddles thumbs

That's about it. Hope you enjoy!

My Little Pony: Friendship is Magic (c) Lauren Faust, Hasbro
Erebus (c) legally-psychotic.deviantart.com
Amani & Art (c) Myself