Accolade

Accolade is a short story by Cereal Velocity. It centers on an attempt by Trixie and Luna to get revenge on Twilight Sparkle.

Summary
Despite feigning indifference and gratefulness, respectively, neither Trixie nor Luna have quite gotten over the humiliation dealt them by Twilight Sparkle in Boast Busters and Friendship is Magic, part 2. Trixie also appears to have repressed desires for her rival, though this does not stop her from agreeing to a plan that is likely to end in Twilight's death; she is, in fact, the one who initiates contact with Luna.

Said plan involves Trixie becoming Luna's apprentice, getting taught everything Twilight has learned from Celestia, so she can best her in a duel. That would remove Twilight as a reminder of Trixie's sole failure, and it would remove an obstacle to Luna's path to the throne; without the Element of Magic in her way, she thinks she'll be able to topple Celestia.

Luna tries, but fails, to keep Trixie's presence in the Canterlot palace a secret from Celestia. It is unclear how much of their arrangement is known to her older sister. The only thing Celestia is letting on is the assumption that Trixie is Luna's girlfriend, stashed away in various rooms in the palace so they can have secret nightly trysts. Celestia's attempts to accomodate her sister, like sending food to what she thinks is their "study room" or switching practice objects with pornography, are played for laughs.

During what Luna has determined will be their final practice session before Trixie will be ready to kill Twilight Sparkle, she notices Celestia watching them from outside. To get the alicorn to leave them alone, Luna pretends to caress Trixie and eventually kisses her. Trixie is surprised at first, but then she doesn't just play along, she returns the gesture. Luna goes even further by playing around with Trixie's horn, but when it finally looks like Celestia is about to leave, Trixie jumps up angrily. She accuses Luna of not having any real interest in getting revenge, and that she engineered all the practice sessions so she can get Trixie into her bed. She renounces their pact and teleports herself out of the palace. Celestia pretends to have accidentally overheard the commotion and "comforts" her sister by saying that Trixie wasn't really her type anyway.