Dragons. Maybe the Dragon from Dragonshy gets tired of their attempts to force him out of his cave, maybe Princess Celestia steps in when it gets out of hands… and it escalates from there? Maybe it draws other dragons?
Equestria 2–Deviations; Blueblood is chosen as Celestia’s student, Nightmare Moon is reformed out of her sheer annoyance over Blueblood’s selfishness and banishes him to the moon before making up with Celestia.
Equestria 3–Reflections; King Sombra resists Imperator Celestia and Luna’s tyrannical conquest of Equestria.
Equestria 4–Sombra War; Rainbow Dash is prevented from performing the Sonic Rainboom by Starlight Glimmer, years later King Sombra gathers an army to go to war with Celestia and attempt to revive the Umbrum.
Equestria 5–Changeling Takeover; Starlight Glimmer convinces Hoops and Dumb Bell to stop bullying Fluttershy, years later Queen Chrysalis and her changeling hive take over Equestria, with Fluttershy, Pinkie Pie, and Zecora leading a ragtag resistance against them.
Equestria 6–Eternal Night; Rainbow Dash, Hoops, and Dumb Bell become distracted by a battle between Twilight Sparkle and Starlight Glimmer and don’t race, years later Nightmare Moon brings eternal night to Equestria and employs Rarity as her loyal maid and Rainbow Dash as captain of her royal guard.
Equestria 7–Tirek Armageddon; Starlight Glimmer trips up Rainbow Dash during her race with Hoops and Dumb Bell, years later Tirek absorbs the alicorn magic and uses it to lay waste to Equestria.
Equestria 8–Reign of Chaos; Rainbow Dash is frozen by an accidental magic blast by Twilight Sparkle, years later Discord is freed from his imprisonment and turns Equestria into the chaos capital of the world.
Equestria 9–FlimFlam Industrialization; Starlight Glimmer assists Fluttershy in being a better flyer, years later Flim and Flam are granted permission to tear down Equestria’s forests in favor of their goal of total industrialization.
Equestria 10–Daybreaker Apocalypse; Starlight Glimmer shoots Rainbow Dash out of the air during her race with Hoops and Dumb Bell, years later Luna is killed when she and Celestia attempt to confront Queen Chrysalis during the Canterlot wedding. Consumed by rage and sorrow, Celestia gives in to the Nightmare within her and transforms into Daybreaker, slaughtering Chrysalis, Cadence, Shining Armor, and everypony at the wedding before unleashing a brutal wave of apocalyptic destruction across the world. Upon seeing Twilight, Spike, and Starlight enter her domain, Daybreaker now knows that there exist other Equestrias apart from her own in other realities that have not been blessed by her divine flame, and seeks to spread her destructive power to all Equestrias in the multiverse and beyond…
@Yet_One_More_Idiot: It wouldn’t have been the first time an omnicidal maniac has appeared in this series. If what the “Nightmare” part of Nightmare Star’s name implies is what I think it is, then we may have seen said omnicidal maniac appear intwo(maybe three) forms by now, and that’s another timeline where it’s prominent.
Something really powerful and evil, or nothing at all; so many things in fiction can turn a country into a barren wasteland, so many it would be pointless to try to list them all.
And I seriously doubt Celestia has anything to do with it, there’s no reason to think even a “nightmare star” would simply destroy everything when she could be basking in glory like the eponymous card game item shows.
@Pepsi_Al
The details are obviously sketchy, since some timelines end with Discord in power and some don’t, despite the fact that the only way the ponies can fight him is with the Elements of Harmony.
@Background Pony #25F1: The problem with that is that each timeline shown here happens as a result of Glimmer preventing RD’s Rainboom from happening. No Rainboom, no Element of Magic, as finding it is one of the results of said Rainboom. And Sunset brainwashing as many people as she could find, IIRC, depended on her getting the Element of Magic.
