Okay, so I just finished my synopsis for the story.. It took a while, but I feel like I'm getting somewhere with this!
Synopsis down below!
The main group of friends travel to find the First Order of Alicorns, who have been trapped in the Realm of Darkness -guarded by Lavan- for thousands of years.
Catrina, an all powerful witch, was close with the First Order, and gave them each large supplies of Witchweed, which helped them complete their tasks for each season they looked after. After Lavan captured them and threw Equestria into chaos, Discord had defeated Catrina, stealing her amulet and beginning his reign. After Discord's defeat, Tirek had found the amulet hidden under Canterlot and began his reign, only to be defeated by the Princesses as well, leaving Star Swirl to give the amulet to Scorpan after completing several quests to prove he could protect the land.
These four Alicorns in question, had kept Equestria in balance. They created an empire, where they each controlled a region of the land, each region fitting the theme of their powers. Their sudden disappearance had thrown Equestria into a state of chaos and disorder, leaving these Alicorns to leave behind six trinkets, The Elements of Harmony, to protect the empire and keep it in balance as long as they were protected. These events caused Star Swirl to call upon new leaders of the land and bearers of the Elements, Celestia and Luna.
A few hundred years after the School of Friendship's success, a new group of students, who call themselves the Mismatched Society, are sent by the Friendship Map to a strange land, believing it to be a friendship problem. Twilight finds a new set of elements, which Star Swirl kept in his wing in the Castle, called the Elements of Unity.
With the group and Discord, who Twilight had chosen to accompany them, the First Order are eventually found to have been imprisoned for so long, that they've withered away and their magic spread across Equestria. Lavan, who has been working on taking over the land one region at a time, has gained access to Scorpan's amulet, who he had originally obtained from Catrina.
After gaining the amulet back and working together, they eventually defeat Lavan, and despite the balance of Equestria not quite being how it should be, it is safe for yet another thousands of years.