NOTE:

Because my AU been in the work for years, just not published, there are some things that conflicts with the canon, especially with season 9. One of them is Sombra.

While overally my AU ignores things in the comic, one of the things I did adopt is their interpretation of Sombra (his backstory, Princess Amore, the umbrum, Radiant Hope, ect). So most of the story from Fiendship is Magic (the Sombra issue) and Siege of the Crystal Empire is canon in my AU.

But ever since season 9 happened I thought a lot how could I include some of it. As in case of Sombra, he got a different fate and personality than in the comics.

So after some brain storming, here's the story:

(btw timeline as is: Siege of the Crystal Empire —→ Season 9 opener)

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When Sombra was destroyed by the Crystal Heart parts of him (let's say his essence) was scattered in the ether around Equestria. Most of it however stayed inside the last remaining physical part of Sombra, his horn. This is how Radiant Hope managed to revive him. Let's call this Sombra 'Sombra Prime'. He is the one who later decided to choose his fate, banished the umbrums again and in a new reformed body went on a years of quest with Radiant Hope, to find the shattered parts of Princess Amore.

However, as said just 'most' of Sombra's essence stayed within his horn. Few, small spieces stayed around in Equestria. One of these essence was used by Discord to revive a new Sombra (let's call it 'Sombra Fragment') for his plan as a 'confidence booster'. Sombra Fragment is not a full. His memory is fragmented (for example he barely remembers Radiant Hope). It also can be seen his personality, which is simple and unchanging. He is that dark part of Sombra, who enjoyed being a tyrant. While not full, because of the magic of umbrums, still powerful.

When Sombra Fragment was destroyed he became an essence again, floating nothingness. Years later, when Sombra Prime was traveling for his quest, Sombra Fragment find him and got attached to him. However, because Sombra Prime became more pony now than umbrum, Sombra Fragment couldn't become part of his again. So he pretty much became a ghost that hunts Sombra Prime (who is the only one who can see him), manifesting himself in mirror and waters as a reflection. Sombra Prime couldn't help but view him as punishment for his crimes of the past.

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There's more little tibbits, but this the gist of it. It's already ended it up pretty long. Hope my ramblings are coharent enough.'''''

Also, on this pic Sombra Prime is older, his in his 40s. And Sombra Fragment doesn't age.