Sombraverse

The Sombraverse is an alternate reality version of Equestria created by Starlight Glimmer through the use of her Chrono Trigger spell and the Cutie Map.

History
The history of the Sombraverse was presumably identical to that of the main timeline of Equestria up until the day on which the Mane Six were supposed to receive their Cutie Marks. Starlight Glimmer, seeking to prevent this from happening, traveled back in time, but was pursued by and. Unaware of her plans, the pair were unable to prevent her from interfering with the race in which was supposed to perform her first Sonic Rainboom, halting the filly with her telekinetic magic. As a result, none of the Mane Six received their Cutie Marks, and Twilight and Spike then found themselves drawn back to a drastically altered present.

Due to Starlight's actions, this alternate Equestria saw Sombraverse King Sombra succeed in retaking the Sombraverse Crystal Empire, and forcing all the Crystal Ponies to serve as his Sombraverse Troopers. With this army at his back, Sombra launched an assault on the rest of Equestria, resulting in the Great Crystal War. At the time of Twilight and Spike's arrival, he had managed to seize control of half of Equestria despite the brave efforts of Sombraverse Princess Celestia and the Equestrian Resistance. Much of Sombraverse Ponyville was shuttered up, and Sombraverse Sweet Apple Acres was converted into a factory as part of the war effort.

Upon meeting Sombraverse Applejack, Twilight explained how she had come to be there, and was then informed of the state of affairs by Applejack. These included Sombraverse Rainbow Dash, Sombraverse Pinkie Pie, and Sombraverse Maud Pie serving as soldiers under Celestia, while Sombraverse Fluttershy and Sombraverse Rarity operated in other areas. Rarity had notably relocated to Sombraverse Manehattan to help produce uniforms. Horrified by this altered reality, Twilight and Spike set out to restore the past to normal, presumably negating the Sombraverse from existence when they traveled back in time.

My Little Pony (Gameloft)
In Gameloft's "The Cutie Re-Mark: Sombraverse" and "Sombraverse Redux" events, and Babs Seed learn of the Sombraverse timeline from Starlight Glimmer while the latter is working at the School of Friendship. Scootaloo, who had recently been accepted as a tutor at the school, wanted Starlight's help in dealing with a feud between two of her friends, one from Ponyville and one from the Crystal Empire. In response to Starlight's reluctantly shared information, she imagined Twilight battling Sombraverse Troopers alongside the Sombraverse versions of Rainbow Dash and Applejack. Babs, who was genuinely excited in learning about Starlight's time travel escapades, asked her about the Sombraverse, and imagined Twilight fighting the Sombraverse Troopers alongside the Sombraverse versions of Maud Pie and Fluttershy.

Behind the scenes
Little is known about how the history of the Sombraverse unfolded differently than that of the main timeline. This reality presumably involved an altered version of the events of "The Crystal Empire" in which Sombra was not defeated, due to Twilight Sparkle never becoming Celestia's student and recovering the Crystal Heart with aid from Spike. This timeline also seems to have not included the redemption of from her time as Nightmare Moon, given that she does not appear.