Background Information/Prologue:
(This chapter is not story material, it is simply information that will benefit the reader, before going into Chapter 1. Chapter 1 is where the narrative starts)
Mushroom Kingdom: After the war with Galeem and the disbanding of the Smash Bros., Mario went back to his kingdom, to relay the news of his adventures with the Smash Brothers, and the death of his brother at the hands of the light Titan. Peach, due to the revelation of other possible alliances, such as Hyrule, Dreamland, Mute City, etc., reaches out to said kingdoms, in order to strengthen the kingdom's defense. It was no secret that the kingdom was woefully understaffed in the military department, and as such, these alliances were key to preventing further war and turmoil.
It has been 2 years since then, and Mario has settled down, going on small quests here and there when he pleases. He constantly is reminded of the times he spent with his comrades during their adventures against Galeem, and while he is soured on large adventures due to his age, he does yearn to reunite with them someday. What he didn't know was that his desires would be granted, and not in the way he wanted...
Hyrule: After the battle with Galeem, Link returned to Hyrule Castle, worn, and tired, after the massive journey he'd just taken part in. Being over a century old didn't help to ease the strain of his activity. Zelda, one day, asked of what his journey entailed. Link responded, but much to his detriment. In realizing the amount of near death situations he'd been involved in, she could no longer, in good conscious keep him under her service. Had he been killed, it would have been on her, due to the fact that she approved his joining of the Smash Brothers. She retired him from being a Champion.
He now spends his days living a peaceful life in his Hateno house, much to his resentment. Link wants, more than anything, to fight for Hyrule. He had never known anything else. A fight, however, was coming to him...
Sanghelios: Arbiter, had managed to win the Sangheili Civil War, and has since, took the mantle of ruling the Sangheili people. However, his days of fighting intruded upon his governing days almost as soon as they had appeared. Strange portals, housing creatures he'd never seen before started to appear on his home world, and caused much havoc. He joined the fight against them, his forces going so far as to developing a device that could track where a portal appeared, however, his attempts were futile. The portal attacks eventually ended, upon calling an old ally, John-117, he realized that Sanghelios was not the only world experiencing these attacks.
He gave the throne to his second in command, Rtas 'Vadum, and embarks on a journey to find other worlds that are being attacked, gaining warriors, and aiding their cause.
Dreamland: After the war with Galeem, Dedede, is sent into a spiral of self reflection. He had his days of villainy, before the era of Galeem, and desperately wanted redemption. In a few of Kirby's quests, he had tried his best to aid the pink warrior, but it wasn't enough. Not until Galeem. Once the threat of Galeem rose, he realized that his redemption was tangible, and he threw himself at the efforts to end the light titan.
However, even after the war, he felt he needed to do more. He built up his forces of Waddle Dees and had them trained extensively by the Meta Knights, should another threat ever require their use. He was ignorant however, that the need for his armies were to come very, very soon.
Skyworld: Classified
Hylia's Domain: Classified
Portal World: Classified