As you can obviously can tell, Eagle-Beak is a Griffin from Camelot. The only reason he's in Equestia was because his family long ago immigrated there. The Beak family became famous for being capable to easily do magic without horns or even much years of extendsive training. Some members of the Beak familiy became great friends of Celestia, all of them were mainly teachers of Magic University. When Eagle-Beak was born, he was.... Different. Having a superiority complex, Eagle-Beak felt he can espire to great things then just being a shcool teacher. He wanted to be the Royal Souccer. But while his parents didn't complain about this different desteny, they warned him that it might not be easily gained. One of rhe Equestian Griffin Kings, King Cedric, while he doesn't hate the idea of griffins doing magic, he has became extremely cautious to the idea of doing it since the worse exsaples of Griffins becoming too greedy and dark with magic are Queen Magi and Sir Sam Mingo. But being supportive parents, they allowed Eagle-Beak to seek out his new passions, but they warned that he needs to seriously earn Cedirc's trust, cause he's known to put a strict eye on Magic capable Griffins and virtually restrict them like a painfully heave ball to chains. By his teens, he was already allowed into Magic Universeity and his magic skills became the talk of the shcool, and earned Cedric's attention.
Cedric was kind enough to willingly offer Eagle-Beak a position with him as a personal soccuer, but wasn't afriad to warn him that since Griffins succumb to greed more easily then even dragons, he's afraid Griffins can't be easily trusted with having magic, being a thing that can demand automatic respect and unlimited power to any desperate enough griffin, and that Griffins who had became capable of magic have automaticly became corrupt and dark. Eagle-Beak assured the King his trust is not ill place and promises he will be respondsable. But Cedric was worried the magic would soon make Eagle-Beak fail to live up to the standerds of the before-corrupted state. Cedric knew something would drive Eagle-Beak to do risks almost no more different then the crimes of Magi and Sam. At first, Eagle-Beak did fine, but then, he discovered something that concern him. He was reading an Equestian History Book when he discovered the Nightmare Moon propicy. He discovered that at a far certain point in time, Nightmare Moon would plunge the world into enturnal night and never let the sun raise again. At first, he was convince that it was only a horror-story. But one bad night, he had a a nightmare/"vision" that it was diffently gonna come true, as Nightmare Moon did returned and plunged Equestia into perpetual night, slowly destroying the land and ending life as it is known. Awaken in horror, Eagle-Beak was now convinced that Nightmare Moon was nothing but a world destorying monster that needed to be destroyed. He warned Cedric about Nightmare Moon. In truth, Cedric is among the only trusted people who knew the truth by Celestia, and was asked to discredit the return as a mere scary myth created by anichent history's nutcases. But Cedric couldn't bring himself to lie to Eagle-Beak, so he informed Celestia about everything. The two seemingly convinced Eagle-Beak that everything was under-control, entrusting him with the knowledge, but warning him that if he attempts to expose it, he will have to be discredited as deludsional. Nobody has since known that it was the fault of Outside Forces.
As much as Eagle-Beak wanted to trust Cedric and Celestia, he knew something had to be done. He didn't believe Princess Luna was in anyway salvageable, so he assumed it was better to destroy Nightmare. And based on what he learned about the Equestian Purple Dragon Realmians Dragon, he needed something as powerful, but stronger. He looked up a Dragon Realmian legend on Scarlet Dragons, and discovered that they are only born in a time of great peace. Eagle-Beak knew that's currently impossable in the times he was in, even in Equestia, so he wanted to create one through another way: actselly make one. He teleported himself to the Dragon Realms, but was careful enough to stay clear of the cross fires of the latest violence of the Dragon-Ape wars! After a Sluaghter has end, Eagle-Beak found a lone egg in where one of end results made a dragon family died. Eagle-Beak desided to claim the egg, and leave the Dragon Realms. He altered the formerly blue egg to become a Scarlet egg, and created what he named "Quidilin". He loved and raised her like his own, but then, because Cedric had a hunch his Nightmare Moon Paranoia would be too great, and had his guards investifate Eagle-Beak. Dispite Eagle-Beak's attempts to deny, he was discovered with Quidilin. He was removed as soccuer and lost costity of Quidilin, with Cedric promising she'll be given to a new loving family having had heard her original parents were lost to war.
Heart-broken his dream was lost because of his fears, he became the original family desteny of becoming a Teacher, which he felt was beneth him. It helped little that the New Generation has indeed grown doubtful of Nightmare's return thanks to Celestia not wanting her sister's name to be demonised and basturdised as a monster. By his adult years, his concerns only worsen when Nightmare's return is still coming, and Celestia is still hopelessly "deludional" that friendship and harmony can bring Luna back. Eagle-Beak desided that Equestia staying peaceful would be it's own undoing, and desided that he is going to what what is nessersary to stop Nightmare Moon.
With help from Clare Buckington and Gary Skalesworth, Eagle-Beak has corrupted weak-willed students into supporting his new plans of turning Equestia into a war nation to counter the return of Nightmare. While the two partners didn't nessersarly believed the Nightmare Moon part, they supported his attempt reguardless. But when the Rebelion did happened, pre-maturely thanks to the interfearence of Celestia who Eagle-Beak assumingly banished to the Forzen North, Eagle-Beak's army weren't able to stop Haku, Princess Candence and Shining Armor to being able to get to the world of the Childhood Guardians, where it's where the main heroes truely ended up being banished too, and defeated all of Eagle-Beak's forces and stopped the Professor himself.
He was sentenced to 10 years in Tartarus for his crimes, where the negitive magic of Tartarus rapidly aged and deformed him from his former grace. Wearing a robe that's considered the usual Tartarus prison garb, he returned to Equestia after his sentence was up, quickly discovering that Nightmare was indeed stopable by friendship and harmony and that he was extremely wrong! Feeling like a paraniod fool, he attempted to make amends with the Equestians, but both Ponies and Griffins gave him a harsh, torturious reception that included pulling some of his wing feathers off! He lost an eye to it as well. But Celestia intervine before things turned fatal and tried to help Eagle-Beak refit into socity, but the broken and hurt Griffin rejected the offer angerly, and declaired that Equestia just made a new enemy?! He left Celestia crying to herself, the mob feeling awful for what they did, and Eagle-Beak becoming the villain he remains to this day. He's yet to be finally contained and defeated.