It's been several months since Pinkie Pie made a stunning admission about her past that permanently changed her relationship with her friends, particularly Twilight Sparkle, but life seems to have settled back to normal (well, normal by Pinkie Pie's standards, at least). However, when an old nemesis returns and ensnares Twilight in her influence, it's up to Pinkie to make things right.
This is the second story in The Petriculture Cycle. There is a TV Tropes Page for the entire Cycle here.
Cover image by Page Turner; "Princess Twilight" vector by Nianara.
Twilight tries to figure out how rock farming works.
When Twilight is taken by the Nightmare, it's up to Pinkie Pie to rescue her.
Penumbra seeks gainful employment.
Trixie returns to Ponyville to challenge Twilight Sparkle. ("Magic Duel" as it occurs in the Petriculture AU.)
Celestia decides to attempt to reform Discord, so she taps a pony with a similar background for the job. ("Keep Calm and Flutter On" as it occurs in the Petriculture AU.)