I’ll be honest, unicorns aren’t the class in MLP that I’m the most fascinated with, but they were the most fun to make headcanons about, so here they are!

Unicorns are the youngest class of ponies/horses, earth ponies being the oldest and pegasi being the second oldest. They appeared thousands of years before the forming of Equestria, which gave them enough time to form their own species. The unicorns, in most cases, are closed in creatures, very secretive and secure. They keep to themselves and don’t like prying their noses in places they don’t belong. Since this was almost the exact opposite from pegasi and earth ponies, they were seen as strange creatures at first. This was until the three tribes were united into Equestria, and all three tribes began living as one. In modern day, unicorns are seen as just another pony to everyone else.

However, the race that took a little more time to accept were the moonicorns. So curved horns and pointed teeth, they were seen as different from, but also the same as the unicorns. Because of Moon Pony history, fitting into society at the beginning of Equestria was a bit difficult.

Though a unicorn and moonicorns horns look different, they are built exactly the same. On the outside, the bone of the horn is wrapped in a soft, thick velvet material. Underage bone is a magical substance called Magic Seep. Should a unicorn's horn be broken, the magic will seep from their horns and for the time being, they can no longer preform magic. The Seep is an infinite fluid, it never stops producing and so if a horn is broken at any point, they will always have their magic. Any horn broken above the bone will grow back and keep producing Magic Seep, but any horn broken past the bone will not grow back. It will still produce Magic Seep, but since the horn would not have as much space, it would not produce as much as before.

In Tempest Shadows case, however, having her horn broken at an early age, she trained herself to be just as strong if not stronger than the normal unicorn with unbroken horns. Still, the loss of Magic Seep can cause electric spasms and sudden burst, both things Tempest has learned to control. She even knows how to channel these burst in combat.

With the amount of electricity that a horn can store, “Horn Frys” can occur if a unicorn's horn overcharges, causing electricity to shoot from their horns. This could cause severe burns and brain injury, which is why most unicorns prefer staying out of the professional magic field. At worst, a unicorns horn could completely shatter, leaving burns on their face and chest area.

Hollow Euphoria happens when a unicorn uses too much magic. This should not be confused with Horn Fry’s, since Hollow Euphoria occurs when a unicorn becomes dazed from casting too many spells and can not tell imagination from reality. Their Magic Seep will run on empty, unabling them from using their magic for about 2 to 4 hours, during this time, they can badly lift a fork.

Moonicorns have sharp, round teeth for eating fish, the only source of meat in their diet. At first, Moon Ponies eating meat was frowned upon in early Equestria, but in modern day, it’s seen as normal.

Unicorns have round, dull teeth for eating plants. Like in the notes, should a unicorn or any Sun Pony eat fish or any source of meat, they could become sick, leading to vomiting and nausea.

Unicorns touch horns to show affection for the other. This is extremely common among family members and even close friends, who would be a bit confused at the gestur. However, touching a unicorns horn would be considered rude, less rude if done by another unicorn.

The Kirin are like a mix of ponies and deer folk(info on them coming soon). They channel their magic through the large, branch-like horns in the middle of their horns. They are very similar to deer folk in appearance, but similar to ponies in personality. Like deer antlers, should Kirin horns break, they will grow back in 2 to 3 weeks.

While unicorns and moonicorns were the last of the pony species to develop, they are the most iconic across the land. If you go to a school like The School of Friendship where there are all sorts of creatures, you’ll most likely see a unicorn representing the pony species.