Takes place during The Game of Life
Vinyl Scratch has been feeling pretty down after Rainbow Dash's death, so she seeks out the help of the alternate universe's Pinkie Pie. After all, no one can make a portal to bring back the dead like Pinkie. But portals like that can be very unstable, and you may not get the results you wanted.

Crossover with the book series Warriors, Power of Three, book 5.

Cover image base: Link