Alicorns + Celestia and Luna origins [description]

Mmmmkay, I'll explain - After drawing this I started thinking further on the subject of Celestia's and Luna's past, so below, I'm going to share my... headcanon-thingy with you.
Please note that I have not read the comics for a while! If there was any new information in them I am not aware of it, so my idea might be wrong. I'd still love it if you'd point it out for me politely - but! I'm not going to change this, so if it's more comfortable with you, you can call this an AU.:3
Here goes:

1. The whole idea came from the breezies and the portal they had to travel through to get home. So, what if there are more portals? Specifically one leading to a different land, the land of Heaven and Hell - Elysium and Tartarus. Elysium is the home of alicorns, they are lead by a king and queen. Tartarus is below Elysium, it is usually ruled by a superior, one every other creature fears.
2. Elysium: The landscape is breathtaking. The whole land itself is like an island, it is surrounded by water, and a water-fall, falling towards the "sky" - it's function is to disable any passing between the two kingdoms. This sea of sorts has a very high magical power - for example, it can heal wounds, even fatal ones. Stories say, it can even bring the dead back to life. The water-fall ends in a mass of clouds. Beyond that is open space - Stars and planets are seen much clearer at night, they are quite close, since Elysium and Tartarus are not really a planet.
   The land is protected from the water by high mountains, they form a wall around the home of the alicorns. In the valley there are hills, forest and fields, and seven rivers by the name of Svöl, Fjörm, Hríd, Sylgr, Ylgr, Víd, Gunnthra. In the middle, there's the world tree, a gigantic ash tree. At it's root is the capital of Elysium, and the castle of the royal family. There are other towns in other locations, usually run by the oldest family. The same family is usually the one that grows food - because it requires one of the highest magical knowledge.
   The kingdom has it's own army, and is usually involved in some form of war - with the creatures of Tartarus. (A longer peace occured during the rule of Queen Pandia.) Elysium tends to think of itself and function as the judge of the other lands, in the name of maintaining harmony. Many stories of Equestria's mythology share the tale of battles between beasts invading the land of 'mortals', and alicorns putting them in their right place.             
   Every 100 years portals open both in Tartarus and Elysium towards other realms - one being Equestria, one with the most benefits for creatures of the underworld. That is, when the alicorns' army is most needed.
   Elysium has it's own kind of money, but it is not such a priority as in Equestria.
   The king and queen raises the sun and the moon, just like unicorns in Equestria. the spell is passed down by the King to his heir.
   
3. Alicorns: Alicorns are highly magical creatures, their powers are one of the strongest. The average age they reach is about 5000 years - they are not immortal, hovewer their body stops aging at some point, meaning they don't grow old. They can be killend and they can die of sickness, but they heal faster than ponies. Before death, they grow very tired, and their magical powers weaken. If they die naturally, they usually pass in their sleep.
   Their long lifespan is caused by their magic. An alicorn can give up it's magic, resulting it having a shorter life - since alicorn magic contains pegasus, earth-pony and unicorn magic, when one gives up enough amount of it's magic, it results them to only possess one of the three types of magic - in short they turn into either a unicorn, pegasus or earth-pony.
   Equestrian ponies can be turned into alicorns, but only by an alicorn and if they possess the certain type of magic - usually the ones that have alicorn ancestors have a hint of it in their blood - alicorns can sense this magic.
   Alicorns live very similar to ponies - they have everyday jobs, but more for the sake of doing something to pass the time, than to earn money. Food is free, it is given to every family according to their needs.
   Alicorns have cutiemarks, but they are a bit different than ponies'. They appear when an alicorn steps into what we'd call "teenager-hood", as a sort of prophecy, (and the illustration of one's soul) for the young to figure out.
   
4. Tartarus: The home of beasts and dark magic. Some creatures were born here, some were imprisoned, some simply stuck by passing a portal - meaning not all creatures who arrive are beasts, but they are usually taken over by one of the parasites hungry for a puppet to control. The land is dry, hot and dark- since it's under Elysium not much light reaches it. The whole land is made of rocky mountains, active volcanoes and deserts. Not much to see here.
   The water surrounds it just like it does Elysium, creating a barrier between the two lands.
   It is usually ruled by one despotic ruler, one who proves to be the strongest of them all. (Exception is Tirek's and Scorpan's reign, when they took over the throne together, the only time Tartarus had two rulers.) In this kingdom everyone has to cope on their own - they fight to survive.
   The connection between Equestria and the two land is the strongest here, the barrier separating it is the easiest to break, however it is still nearly impossible - but not completely.
   Just like in Elysium gateways open every 100 years to other realms- the most tempting for dark creatures being Equestria, because it is one of the worlds that contain strong magic. Beasts try to hide in Equestria, but most are thrown back right where they came from by the alicorn army.
5. Tirek and Scorpan: They are not related by blood, but they were raised as such, by Tirek's father. in a land that's neither Equestria, nor the two mentioned before. Tirek was cast out in the aftermath of an unfortunate event, and Scorpan decided to follow his brother in his exile. In their travels they landed in Tartarus, where Tirek, who was always hungry for power, saw an opportunity to take over the throne. The plan succeeded, and the two brothers became the rulers for centuries to come.
6. Phoebus and Pandia: Phoebus was born in the royal family, he has been raised as the future heir of the throne. When he reached the right age, the King and Queen wanted him to marry one of the nobles' daughters. He picked his childhood friend, from one of the farthest town's noble family. At first everyone was against the idea - even Pandia, she said she did not want to leave her family, and she had no idea Phoebus had such feelings for her (not that she didn't for him, tho). Phoebus calmly brought up the idea of Pandia spending a month at the capital, and after that, they'd discuss the matter again. No need to say, Pandia's feelings grew much stronger during this month, and the King and Queen discovered a strategic genius in her, behind the hot-headed, wild, tomboyish mare.
   So they got married.
   After the King's death, Phoebus took his place on the throne, and ruled side by side Pandia. He put his wife in charge of the army tactics, however he was the one to negotiate with other lands (of course after they talked over the tactics), because Pandia couldn't have stayed calm during these argument, and resulted the danger of the war they tried to avoid.
   They created the longest peace in Elysium's history.
   After a while, they decided they wanted foals. They had two daughters, Celestia and Luna. What not many know, is that there was to be another foal - but it was complicated from the start, and it caused both the little one's and the mother's death.
   The event resulted Phoebus to be incredibly protective over Luna and Celestia. But the two misfits had other plans for their father.
7. Luna and Celestia: A very mischievous duo. They loved pranks, and getting into trouble in their younger years. One of these adventures went wrong - they found a portal, and on the other side, another land, Equestria. Tia being the curious and a bit reckless one, wandered off, much to the disapproval of Lulu. Of course they got lost. The ponies they met had no idea where the portal was, and so, before they found their way back, it was closed again. They were stuck. The four leaders of the land (the founders) decided to take them in, they were more than curious about them, and charmed by their personalities. So the sisters learned about Equestria, and taught the ponies about alicorn magic. They made friends with Starswirl the bearded, and both were amazed by the other's magical powers. The sisters learned the spell the unicorns raised the sun and the moon with (they haven't reached the right age back in Elysium to know it), and offered that they'd do it for them, since they could do it by themselves, while the unicorns had to do it in large groups. After the four original leaders started to grow too weak to guide Equestria, they decided to make the two sisters, who've grown both in knowledge and heart, to be the next rulers of the land.
   After much thinking the two sisters accepted the offer with hesitation. Celestia soon grew confident, but she failed to notice her sister's anxiety. Years passed, eventually a hundred since they came to Equestria - the portals opened once again, and beasts came from Tartarus. But not only them. So did the alicorns, and Phoebus was surprised - and unspeakably happy - to find his daughters. There was a lot of catching up, but they knew it was also goodbye for at least another 100 years, Celestia and Luna could not have left their subjects behind. To protect his daughters Phoebus cast a powerful spell - The Elements of Harmony. He taught his daughters how love and friendship was the most powerful protection, and gave them a seed from the world tree he cast the spell on. He promised them, that they'd be safe, and they will understand once the tree is grown, but they had to plant it at the exact location where the magic is the strongest in Equestria. This plant later turned out to be the Tree of Harmony.
8. References: I took many ideas from greek and norse mythology (world tree, the seven river's names, etc.). This is an unholy mixture of the two. Sorry if it hurts your brain...xD

Awhmyglob... This was so long to wriiiiiteeee... I need sleep now...
Opinions are welcome, so are your headcanons. Sorry that this turned out to be this long.xD I have no strength to say more and to think more...