The way I see it, Alicorns were once a numerous breed that existed a long while ago. It’s quite possible and highly speculated that they are the origin of where the different pony breeds came from, but no one can be completely sure.
Their characteristics consist of them having long, curved horns, large wings, and a slim body, sometimes almost deer-like. They are unnaturally tall, the tallest among all the equine breeds, and their appearance can vary in terms of having cloven hooves and/or long, lion-like tails. Their most defining trait, however, resides in their magic; the alicorn harbors all three types of magic from the three separate breeds (some were known to also harbor Crystal Pony magic as well), as well as their own type of magic: Alicorn magic.
An Alicorn’s magic literally circulates throughout the entire body, from hooves to wings to legs to the body itself. Their signature magic also is within the entirety of the body, although it’s more concentrated within the skull and horn. Alicorn magic is, while not evil, inherently dark. There have been several instances where mortal ponies attempted to use alicorn-based magic or alicorn magic-based items, and every account has been proven to corrupt the user by the sheer amount of power alone. Only alicorns, naturally born ones and “ascended” ones, may be able to handle this sort of magic without risk of corruption by default.
Due to their range, alicorns are, by far, the most magically inclined equine by default. Sadly, most of the alicorns died out long ago, with only a very very select few still living (the only four known ones being the Princesses).
Now, there are two types of alicorns: naturally born, and Ascended.
Naturally born alicorns, like Luna and Celestia, are powerful, heal fast, and immortal to age. However, when I say “immortal”, I mean they simply won’t die of old age; once an alicorn had reached a certain age, it’s body literally stops aging from then on to remain forever young. However, that’s the extent of their immortality. Regardless of not being able to die at old age, alicorns are still able to die through other methods, such as terrible sickness (they are relatively immune to certain, common illnesses), an accident, or be killed. It’s simply not easy to kill one.
Ascended alicorns, however, are alicorns who are artificially created, or a pony who was once one breed that has been transformed into an alicorn (such as Twi and Cadence). These alicorns, while obtaining all three types of magic, tend to be weaker than their natural born counterparts. Their magical strength tends to favor the breed they were before being ascended. For example, Cadence has stronger pegasus magic because she was originally a pegasus. Twilight is a special case, however, in that she is the bearer of Magic and, as such, has substancial strength in every type of magic (especially unicorn magic). Unlike naturally born alicorns, Ascended alicorns are NOT immortal. Their life periods extend a couple of centuries, yes, but they will eventually die of old age. And just like naturally born alicorns, those who are ascended can still die through other causes.
Due to their scarcity, unusual appearance, and power, the Princesses are often dubbed Demigods. This is only somewhat true, specifically in Celestia and Luna’s case. Unlike previous alicorns, they are linked directly to the Sun and the Moon, respectively, and they act as “keepers”. Their bond with the sun and moon gives them their unique, etheral appearance, which only further solidifies some ponies’ religious practices. This religious practice in particular is known as Celestialism, or the worship of the Alicorns (especially the princess sisters) as living deities.
In the case of Rosetta, however, she is literally a goddess. The Goddess of Creation, to be exact. She has immense power far too vast to measure and is immortal in every sense of the word. As in, she cannot, and willnot, die. She, along with the other main gods (the MLP Dev Team), are the ones who constructed and molded the MLP world as we know it, as well as created the life that lives in it. However, of the Gods and Goddesses, Fausticorn is the princess of them all, similar to that of Zeus in Greek Mythology. Iridia (Bonniecorn, although she isn’t shown here) is the Queen of the gods and goddesses, as well as the Goddess of Origin. She is where everything started, where the basic concepts that the rest of the gods use and mold come from. Without Iridia, Gaia wouldn’t have even begun.
The gods generally don’t interfere with the mortal world they’ve created, and Fausticorn is no different. What they do is act as guides when it’s needed, but how that manifests depends entirely on the situation. How often that happens can widely vary as well. Overall, though, the nature of the gods and goddesses existence is unknown other than them being higher beings and the origin of the universe.
Also, a little fun fact; despite having the appearance of an alicorn, Iridia and Rosetta aren’t actually equine. Like all gods and goddesses, they don’t necessarily have a set appearance, as they are powerful enough to mold and shape themselves into whatever creature they wish. However, each god has their own personal preference of what physical form they typically take, when they take one anyway. Iridia and Rosetta tend to prefer the form of an alicorn.
WHEW! That was a bit of a mouthful. o3o There’s still quite a bit of stuffs I could say here, such as other religious practices of Gaia and stuff, but I think I’ll just leave it where it is for now. If anyone would like to know though, or you simply have a question, feel free to ask. And as always, thank you for stopping by to take a look at my stuff. C: