His name is Cosmos, middle brother to Celestia and Luna and the Prince of Harmony. He's short and sturdy and warm and inviting, this alicorn's power resides within maintaining balance, harmony, and his very being is tethered to the world Gaia (like how Celly and Luna's beings are tethered to the sun and moon respectively). I haven't fully figured out all of his abilities, but I'd say his magic is closely tied to the earth and as his sisters are the living embodiment of their celestial bodies, Cosmos is the living embodiment of harmony. He is also the origin of the Elements of Harmony, of which came about around the time Discord showed up: Cosmos' exact opposite.
Even with the combined strength of all three siblings, Discord was simply too powerful to be stopped in his quest to spread excessive chaos (upsetting the world's balance), so in order to put a stop to the Dawn of Chaos, Cosmos sacrifices himself and used his magic and entire life essence into forming the Tree of Harmony. From this came the Elements of Harmony, purified and concentrated magic in the form of crystal gems that represent the aspects of harmony: Honestly, Generosity, Laughter, Kindess, Loyalty, and Friendship (otherwise known as Magic). No longer restricted by the physical limitations of a flesh and blood body, the power of Harmony for the first time could be fully utilized by Celestia and Luna to defeat Discord and imprison him in stone: a fitting parallel, considering the fate of their brother. The sisters vowed use the Elements of Harmony only when absolutely necessary, and until then the Elements would remain within their encasing of the Tree of Harmony, safe and tucked away until it is needed.... and maybe, somehow, find a way to revive their brother??
All of this came about from the idea that the Elements of Harmony hold some level of sentience, in which not just anyone could use the Elements... they had to be chosen by the Elements. This is why Luna, when she became corrupted and turned into Nightmare Moon, could not use her half of the elements: the Elements no longer deemed her worthy of wielding them, and as such rejected her. So, why not have the Elements' consciousness... or semi-consciousness come from the unused concept of their long lost brother? C:
Some mini-ideas for him:
-He’s the middle kid of the alicorn trio
-He fuckin LOVES donuts
-His mane actually doesn’t float unless he’s using an excess amount of magic. Otherwise it reacts to gravity like that of a normal pone’s
-He's the shortest of the three. He smol boi
-Gentle, nurturing, amiable, patient: he doesn’t get angry often, but I can see him as being something of an airhead. He has a soft lulling voice and gives off a calming aura
-Makes for a lovely pillow; he floofs up quite a bit.
-When he walks, flora sprouts beneath his hooves before fading away
I might've jumbled up some stuff in there so if you have any questions feel free to ask!
Then I got to the part where he essentially sacrificed himself and I very nearly burst into tears.
I wouldn’t mind seeing some backstory of him in the future (ironic wording), where we can see him with his sisters. Or, perhaps if there’s stuff in the future like this, where we see him revived. . .
I agree that the Elements choose the wielders and have some sort of magical sapience.
I like it wow
I love him.
One, how does he fit in with what we learn about the Elements in Shadow Play?
Two, how does he fit in with Twilight's purpose as Princess of Friendship?
If neither of these apply to this particular headcanon, go ahead and ignore me unless you find the questions interesting.
Cosmos, given he is essentially the Tree of Harmony and the Elements of Harmony are extensions of that, is the direct reason the Mane 6 are the Bearers. They were chosen that fateful day (the rainboom incident), based on each of them being the living embodiment of the Elements they will soon receive: Magic, Generosity, Honesty, Kindness, Laughter, Loyalty. So in part, Cosmos is the one that put the Mane 6 on the path of destiny they now tread, to become the new keepers of Harmony. Twilight becoming the Princess of Friendship wasn't necessarily his doing though; that was Celestia and Luna giving her a title to work with once she entered the political space of Equestria and, eventually, the world. And it isn't like they're wrong: Twi's the Element of Magic, basically friendship since friendship is magic in its own way, so it only makes sense her official title is the way it is.
Some of this is subject to change though, since it's mostly off the top of my head.
(The following is only if you're at all interested in the very basic concept of the Pillars, and could find some use for them that you'd enjoy more.)
In regards to Cosmos' relation to the Pillars? Well, you're not missing too much in regards to their purpose; but how they were used was pretty cool. In canon, The Pillars of Old Equestria are, basically, My Little Avengers and Proto Elements of Harmony. Their Elements were Strength, Beauty, Bravery, Hope, Healing, and Sorcery. Prior to the event with the Pony of Shadows, they planted the seed that eventually sprouted into the Tree of Harmony, and you probably know how that turned out. The cool part was seeing these legendary heroes teeming up with the Champions of Harmony. Though Star Swirl was kind of a dick. Like, even for a Canterlot native. His knee-jerk reaction to anything he can't figure out is to just banish it. No friendship magic, no chances for redemption, just kicking the problem out so someone else can deal with it. The Sirens were not a one-time deal.
And that is pretty cool, I have to admit; I like the idea that the Elements take to what virtues are needed at different times... or maybe there are different elements at play aside from the elements of harmony? It's something to consider for sure! I did hear a lot about Starswirl being a huge ass though; I think it's kinda interesting, seeing how some of the problems Equestria has now kinda stemmed from Starswirl being unwilling to try and understand or even befriend something.
From the way it was explained in the episodes, it sounds like the Pillars have their own set of Elements, and the Elements of the Champions are derived from there. The parallels are mostly obvious. Strength/Honesty, Beauty/Generosity, Bravery/Loyalty, Hope/Laughter, Healing/Kindness, Sorcery/Magic. The main difference is that the Elements of Harmony were intended to be used together from the get-go as the recipe for Friendship Power, while the Elements of the Pillars all just happen to work well as a team. It's possible they all knew they could never wield the EoH themselves, on account of Star Swirl's ego and borderline xenophobia(a topic they saved for the antagonist of the S8 premier. It sucked.), but that has yet to be even mentioned again.
Also Star Swirl being a xenophobic problematic hero makes things a lot more interesting... I might have to give the episode a watch to fully see how it all works before I decide whether or not they're in my headcanon, but thank you for telling me all of this stuff! c:
I hope that you have a great and blessed day/night!
Celestia was able to use the Elements to banish Luna to the moon because the Elements allows her to; it recognized the dire situation, but as soon as the deed was done, Celestia too lost her privilege to use the Elements. Celestia is not blameless in this situation; she may not have known what exactly was happening to her sister, but her behavior toward Luna contributed to her turning into NMM: arguing with her, brushing off her concerns, pushing her away, outright ignoring her sometimes. Both took for granted the importance of Harmony one too many times, and in doing so, did not see the consequences until it was too late: Luna fell to the corruption eating away at her mind, and Celestia lost her sister, unknowing as to whether or not she'd ever get her back at the time.
The backstory is touching on how he acted to save his homeland along with the two sisters, also about his looks also deserve more attention. Even this guy with a beard makes him a lot better