So my idea is what I belive Black and White is with Keyrum, in CUSTOM Dark it's Drakonite, a Dark/Dragon type pokemon the has too much darkness even Darkrai can't rival it, in CUSTOM Light it's Lidronite, a Light/Cosmic type, and in Dusk to Dawn, the fuse and make Dragodracite, the first pokemon to have 4 types at once, it's a Dark/Light/Cosmic/Dragon type. And the only Pokemon capable of rivaling it are Ogerpon and Deoxeys. So in the game basically you play as the champion of the Paldea region and fly to the region in these games and in the lore for how Ogerpon gets there, she kinda just secretly got in your backpack and runs out of the plane when you get there and your 2 quests will be to get the gym badges there and find Ogerpon. Though the Pokemon lore has Teralizing everywhere, to make the lore for why you can't teralize, you forgot your teralizing orb at home. Sorry for the big leak.