Well here’s my concept of Fire Emblem Descendants, where this one is in fact an anime, it is created by some of the animators of the pokemon anime.
Thousands of years ago prior to the beginning of Descendants, the people in the continent of Enualon once lived in peace and harmony with the manaketes, and other mythical creatures where they could control the elements. Until one day, a dark magician named Uchumo who is also a shadow dragon lead an army decided to rule the world with an iron fist and destroy everyone in their way. So the people who happened to be the descendants of the 15 heroes fought back by summoning heroes and their allies from other worlds to trap the evil ones forever, ultimately they won, but then the elements went out of balance. Their allies were went back to their worlds and the mythical creatures were sucked into a crystal for thousands of years, all except for Tiki, Fae, Myrrh, Nowi, Nah, Selkie, Velouria who were left who are now stuck in Enualon, they have no effect of the elements power. So they have to protect the continent from anymore danger now that they assumed the Shadow dragon is defeated. As time passed Tiki, Fae, Myrrh, and Nowi grew elderly while Nah, Selkie and Velouria are now adults.
Until now, when our main hero Marco a farmboy who is the descendant of Marth, he has a pet horse named Fido and he also tends to break the fourth wall very often dreamed of becoming like his great great Grandfather someday, while his mom Mikala gives him some eggs to deliver them to Tiki who lives at a mountain, until various members of the cult happened to follow him, and when they did they brought back Mythical creatures and monsters to Enualon after being sealed for Thousands of years and Marco was being saved by Marth and Caeda who were dragged from their worlds
Only for Marth and Caeda to discover that their descendant, Marco and discover that they’re in the modern era where Marth and his allies have a little curiosity with modern technology, it’s up to Marco and Marth as they across the continent to rally support from other descendants of the 15 heroes and heroes from the otherworldly nations of where the 15 heroes are located to defeated the evil nation.
Season 1 includes characters from Shadow dragon and the blade of light and Gaiden
Season 2A includes charcaters from Three houses, Path of Radiance and Engage
Season 2B includes characters from Awakening and Genealogy of the Holy war
Season 3 includes Characters from binding blade, blazing blade and sacred stones
Season 4 the final season includes characters from Fates, radiant dawn and Thracia 776.
And since it is also created by the same creators who did the pokemon anime they would include some pokemon characters and there’s gonna be a lot of references from movies and other tv shows