Return of King Surtr

The Lodgers and Mane Heroes feel tremors all over Equestria, and discovers that the source is coming from the Norse land of Asgardia, which is far different than how it was when they were dealing with Blackflame, as it's been overrun by jotnars, who are giant godly trolls thought to have been wiped out, who are enslaving the native sleipnirs. They find their leader King Runestone has been overthrown and gone missing while the jotnar's ancient leader, King Surtr, has been stealing magic through their main energy source, the life-giving but poisonous eitr. With his best monster, a Utgaroar named Titanic, looking for him, the heroes must find him first and after killing Titanic, they discover that Runestone has revealed that Surtr was thought to have drowned eons ago during the Ragnarok War between the sleipnirs and jotnars, and since he came back stronger, he learned that he got his power from outermost sources. He had found the hidden secret of the Alicorn Titans, who were higher than the Alicorn Gods and their very ancestors that thrived during the Obsidian Wars. Surtr had given them his soul in exchange for the power of an Alicorn Titan. Now it's a challenge to stop him for good.