This is a little piece describing a new breed of changeling in Equestria... the brainlings, who feed off nice juicy love-filled brains. Not as evil as it sounds, though.

The Brainlings

At first glance, these creatures would appear to be normal changelings. However, closer examination reveals otherwise. Like the changelings, they have compound eyes and insectoid characteristics, but unlike them, the brainlings have evolved to take sustenance from brains.

They all have 2-8 tentacles on their head of varying length. Their shells and eyes range from greenish blue to deep purple. All of their heads can open as if on a hinge, exposing their translucent, purple brains. Their brains are rubbery, slimy, and tough, able to withstand practically anything. Their tentacles can interface with their brains, keeping them connected even if they take them out. They have a sort of stomach that they can use to store a living brain and extract love from it. Some brainlings have a massive, clear tummy, allowing them to store lots of delicious tasty brains!

Unlike normal changelings, they can't transform, but their brains can operate pretty much any body effortlessly. As such, they need to be transplanted into other bodies to infiltrate effectively.
If another love-producing species's brain is placed in their empty head, they will eventually shape the body to be more like their original- griffon brains will change the body to have a beak, larger wings, talons, etc.

Their children or nymphs are born brainless unless the mother eats brain matter beforehand, with the nymph's personality being a combination of all the brains eaten. Usually, a small chunk of brainling brains is sufficient, as brainling brains regenerate slowly if damaged. More doting parents sometimes eat massive amounts of brain matter to give their kid the best brain they can.

Their queens look much like a normal changeling queen, albeit with tentacles. One tentacle, at the base of their skull, is made of brain matter and is used to link up to the hive’s Elder Brain- a massive, pulsating brain sitting in a pool of changeling goop, made up of the brains of the hive’s deceased.

Their society is actually pretty ponylike, but with an emphasis on brains- they treat their brains well so as to maximize love production. In fact, most brains held by brainlings are free to go whenever they want, popped back into their bodies if they want to come back to being a normal pony (or given another body should they so wish). They are placed in large goo-filled vats (or the Elder Brain’s brain-pool) where the brains can telepathically link with each other, swim around, and live in a world created from their shared memories.

Empty bodies are reanimated by hocking up goo in their empty skulls- these husks then become the brainlings’ slaves and servants. Depending on the amount of goop in their skulls, they can be either shambling zombies or fully-articulate, if mono-focused, servants.

The Brainlings were created years ago, by a mad unicorn sorcerer. He would kidnap all kinds of species, extracting their brains and feeding them to a magical flower in his garden, then using magic to reanimate the bodies as his slaves.

One beautiful spring day, the flower bloomed. Out swarmed several angry brainlings, miffed at having their brains eaten. They took the sorcerer's brain and put it in a jar- but afterwards they were confused what to do.

Soon they found that they needed the love of others to survive. Some brainlings wanted to steal others' brains to feed themselves. Others wanted their brains to be put into the empty heads of the sorcerer's former slaves and live a life among others. Their first queen offered a compromise- those who wanted to be among others would infiltrate, searching for brains willing to become part of their hive. Those who wanted to steal brains would instead study those who came into their hive willingly, and breed their bodies to make more bodies to pop into and more brains to feed off of.

When her body died, her brain matter was combined with several other brainlings, and became their first Elder Brain. It decreed that her daughters would each rule over part of their kingdom. A chunk of the first Elder Brain was given to each daughter to start their own Elder Brain- and there is where the brainlings are today.