Short little comic of a Mlp au i've got bouncing around my head called "Twilight's Entity"

A Quick summary is that in Season 3, when Twilight went into the crystal empire's Castle to try and find the Heart, there was seemingly an entity trapped within the crystal by Sombra to guard the Crystal Heart, and in her efforts to find it, Twilight unintentionally freed it. It proceeded to latch onto her, deeming her responsible for teaching it how to be Alive, and she begrudgingly does so, eventually coming to see it as a proper friend as it gains its own sense of Self.

This comic comes from what would be the season finale, "Magical Mystery Cure". The finale goes as normal, but the Entity isn't found anywhere, and when Twilight goes back to her Library to look for clues, she instead steps into a void that replays her childhood memories, and after each memory, the Entity's voice can be heard, "What is my name?", something it has asked her many times before.
It isn't until the final memory ends that she remembers who the Entity really is- Midnight Aurora, her imaginary friend from childhood.
After this, Midnight gets a proper physical appearance rather than being a literal shadow of others'.