so i kinda modified Sombra's origin story
rambles below
Once upon a time in Equestria, a brave herd of ponies set out to explore the great Frozen North. Although an artic wasteland teeming with monstrous abominations, the land was also foretold to contain untold treasure for any brave enough to conquer it. After months of mining, the explorers hit upon an underground cache of countless, glittering gems….and only discovered more and more treasure the more places they looked. It was all far too much to bring back to Equestrian civilization….so the intrepid team decided to stay where they were, and founded the city-state that would eventually become the Crystal Empire.
Ponies came from far and wide to partake in the treasure, and colonize the land into something more hospitable. Gems and crystals were so plentiful that entire architectural structures could be made out of them. Celestia appointed one of her students to lead the tentative nation, the first Crystal Queen, Amore.
Unfortunately, in the wake of prosperity, the ponies had failed to notice that the land they'd come to call home was already inhabited. A dormant species had been sleeping within icy catacombs, and now, through the noise of construction and mining, had finally been awoken.
The Umbrum.
Powerful nightmare creatures. Distant cousins of windingoes. Vaguely horse-shaped, rolling masses of shadow and horror. Upon seeing the pony invaders frolicking about in their city built from plundered treasure, the Umbrum attacked, plaguing the ponies with biting cold and horrific nightmares. In the end, however, justice prevailed, as Queen Amore launched a devastating attack with her new magical weapon, the Crystal Heart. As the Empire glowed with renewed love and light, Amore ordered her guards to destroy any remaining Umbrum.
One particular Umbra had managed to survive. A mare. Using the very last of her magic, she transfigured her infant child into the shape of a pony foal, and braved one last journey into the Empire, to leave her son, Sombra, on the doorstep of an orphanage.
Sombra was raised as an ordinary pony, never suspecting himself to be anything different. Other foals teased him for his dark pelt that didn't seem to reflect the Empire's light, but Sombra grew to be relatively well-adjusted, if shy and wary of other ponies. He had one good friend at least, Radiant Hope, and that was all he needed. As a young adult, his strange magical powers earned him the spot of Luna's beloved student (and possibly, secret lover).
Sombra's was very studious, and was most curious about why he looked so different from everypony else. Neither Luna nor Amore could seem to answer this, and the more time passed on, the more Sombra wanted to know his origin. There was no record of his parents in the orphanage, nor in official Empire records. Where did he come from? It burned at him. One day, he ran off to the frozen wastes, hoping to learn something new. He discovers an ancient red crystal-one last fragment of the Umbrum's home-and upon touching the crystal, the truth is finally revealed to Sombra. His true identity as the last Umbrum….as well as the fate of his people.
With his dormant shadow powers now awakened, Sombra loses himself to rage. The crystal ponies murdered his people! His mother! And for what? Shiny rocks? Greedy, rotten, little monsters, all of them-especially that lying wretch, Queen Amore. The new, potent shadow magic begins poisoning his mind, exacerbating his anger and hatred. It is he that should be ruler of this land-it is his birthright! He hatches a plan and acts-stealing the Crystal Heart, turning Amore into a crystal statue, and shattering her to pieces. Now the rightful king, Sombra enslaves the crystal ponies, a punishment for their great evil.
Unfortunately, Celestia and Luna disagree. They descend upon the Crystal Empire with righteous fury, and King Sombra, in one final act of hated, sentences the Empire to a 1000 year curse, before he is finally brought down.
Justic always prevails in the end, see? Although……Sombra seems to have…..said something to Luna during their last confrontation. Something that's got her looking at her sister rather angrily now……
~
A millennium later, the Crystal Empire rises again, but this time, Celestia is prepared. Years ago, a vision in a dream showed her that the great King Sombra would be destroyed by the power of love, so she began taking on new students, in the hope of one being a champion of Love that could combat Sombra. Princess Mi Amore Cadenza, an orphan and direct descendant of Queen Amore, was an obvious choice. Celestia took the young pegasus filly in and trained her extensively, then sent her off on a journey around the world to learn the ways of love and family. Cadence eventually ascended, surprising Celestia (who was fresh off the failure of Sunset Shimmer). This makes Cadence one of Celestia's more successful proto-Twilight Sparkles (she had a lot). When the Empire rises, Celestia places Cadence, Shining Armor, and her young student Twilight in position to defend the land, lining up all her pawns in a gambit that succeeds. Cadence replaces the Crystal Heart, revealing herself as the true Crystal Empress, and Twilight's success in the Empire proved she would be ready for more difficult tasks in the long road to ascension. All according to plan…..
Some character notes (that didn't otherwise fit into the story):
-Cadence's official title is the Crystal Empress, and Shining Armor is her prince-consort (commonly referred to as the Crystal Prince, or even King). She is the Alicorn of Family and Love (all love, not just romantic). She is an empath and highly sensitive to the feelings of others, and can amplify existing feelings in their hearts, perhaps granting a shy young pony the nerve to confess their love, or bathing a sick pony in feelings of warmth and comfort. This makes her a very skilled diplomat, but it also makes her perhaps a little too nosy about other ponies' relationships. She just can't help meddling sometimes-though always with words, never with magic.
-Cadence is an avid devourer of romance novels, the trashier the better. Although she adores her Shiny and is in a committed marriage with him, they are both polyamorous and entertain the odd boyfriend or girlfriend between themselves occasionally (Sunburst was shared between them, for a brief period). She and Shiny are totally that one obnoxious couple that nuzzle noses in public.
-Cadence's favorite music genre is disco, which made her and Discord instant friends. She is also very close with Pinkie, Fluttershy, and Rarity. She shares the Twilight family trait of being kind of a terrible dancer.
-Since Cadence originated as a pegasus, those physical traits were amplified when she ascended (she has lots of floofy feathers, perfect for snuggling)
-Cadence is an excellent singer, and most frequently bonds with her daughters, Flurry Heart and Skyla, through daily singing lessons. She tries to drop her regal Empress persona with her children to be a goofball mom-sticking a spoon to her snout to embarrass Skyla at the royal dinner table is a favorite.
-Years later, following his defeat, Sombra manages to reform (sans horn), and is found wandering the Empire's outskirts in a weak, ghostly form. Cadence takes it upon herself to reform him, and she has some success, cracking through the hate that has all but extinguished any kindness in Sombra's heart. Sombra, now lucid, expresses remorse for his vengeful, tyrannical actions, and agrees to help Cadence in collecting the lost pieces of Queen Amore. Along the way, he befriends a recently released Tirek, and they bond over their dumb pony-imposed "reformations".
~
phew that was a lotta words