Before the universe there was nothing. A few eons later the ancestral spirits have self-created, they created several universes but one ancestral spirit named himself ''Herobrine". Herobrine created a multiverse with 3 universes inside :

Overworld : The overworld is a safe haven, when it's morning the creatures inside live in harmony but when it turns night the creatures (the scared ones) go into their houses and hide whilst the brave ones specifically players and others like golems fight them like it's the last thing they're gonna do. Nether : The nether is a fire-y wasteland with 3 biomes of terror. The first ever creatures in there were piglins - Pigs that were struck by lightning and mutated by the fungus in 2 out of the 3 biomes. Every other mob here like Wither Skeletons, blazes, hoglins etc. Are very hostile, will kill each other and other creatures from the overworld if they found the Interconnection between the Nether and Overworld. End : There lives 3 creatures here - Shulkers, endermen and a dragon. The main island contains the dragon and many obsidian pillars, players have to destroy the pillars first then kill the dragon. Once that's done they'll open a gateway that'll randomly appear around the end island which if entered can teleport you to the outer end-island which has endermans everywhere but also several rare end cities where you can get great loot whilst also killing the annoying shulkers that make you levitate if you get by it's rotating, small, white and gray, floating and going towards you; Shell.

Once the creation was done, Herobrine just kept observing it enjoying it too like a hobby. (Choose your Species!) Players, Villagers or Any Animal like pigs, cows etc.