Pinkie took a hop, skip and a fall straight into the underworld that exists in another dimension entirely.

Now her mane seems permanently popped, her heart keeps ejecting itself from her body, her cutie mark is missing and she's being constantly beset by strange monsters.

Pinkie fell to these monsters, now she has to dance with her heart to save them and herself.

This is an "Undertale" crossover.

Sunset Shimmer almost succeeded in taking over Canterlot High, stopped the Sirens from taking over her new home, and managed to prevent the destruction of two worlds. She feels that she deserves a break and decides to return to Equestria during her summer break. Unfortunately, when she enters the portal she appears in a land that is different from the worlds she's already been to. Now she has to save this world before she can even focus on returning home.

Unfortunately, she's not the only Equestrian that's appeared in this new world, as one of Equestria's most dangerous villains is loose to do whatever he pleases. How will she cope with having to save this new world from Tirek?
(This is a different Skyrim story than my Sombra visits Skyrim story)
(Part of the Universe 13 story series, though reading the other stories is not required)