The Casual Notice guide to the MCU Timeline Part 1
Someone, for some reason, creates a set of six insanely powerful magic stones, any one of which gave its holder the power to rule pretty much everything, but, if all of them are brought together, the person who holds them gains access to god mode and a fully populated map, AND infinite weapons and ammo.
Odin conquers the 9 worlds with the help of his dangerously psychotic daughter Hela, triggering the “Domination” Victory in Civilization. He decides he doesn’t want to be that kind of immortal god emperor, so reloads a later save, locks Crazy Girl away in a pocket dimension (because nothing bad happens when you lock people in solitude for centuries) and bangs out a son, making sure his wife drinks a lot during pregnancy so their son would never be bright enough to become a threat. He also adopts an ice giant baby because Petco was having a sale.
The Kree, a vast, galaxy-spanning empire that spends all of its free time getting into wars with other vast galaxy-spanning empires for murky reasons, takes time out from its busy schedule to visit Earth and create the Inhumans from primitive men. This goes well for about ten seconds until one of the Inhumans becomes a living swarm of CGI bug things that sucks out life force and makes convoluted plans to take over the universe. They lock the swarm away on a soon-to-be deserted planet in a pocket dimension. Meanwhile, the other Inhumans rebel, and start two secret colonies: one high in the Himalayas and the other on the moon.
Ego, the Living Planet, discovers that almost all of the universe is not him, and decides to rectify that appalling situation through a two-part strategy:
He leaves seeds of himself lying around that–on a special signal–would start growing and take over whatever planet they are on.
He bangs a hot chick on every planet with hot chicks in order to give himself enough offspring to something something, PROFIT!
Some humans start worshiping Swarm (above) and create a secret society that would form the basis for Hydra.
Odin and the Norse gods decimate the dark elves, essentially committing genocide. One troopship, led by the Ninth Doctor, escapes and hides in a pocket dimension. Odin has Bor (who never really comes up again) hide the Aether, also called the reality stone, in a place, somewhere.
The Ancient One travels to Kamar Taj to learn magic and wear comfortable, airy pant suits with flats.
Pre-Hydra discovers or invents a monolithic black rock that is a wholly independent creative concept and not at all plagiarized from an older work by Arthur C. Clarke. They uses this rock to contact Swarm and occasionally send him loyal acolytes to murder.
Thanos fails to emerge from his mopey Goth phase and decides his home planet (Titan–but definitely not the large moon of Saturn–that would just be silly) would be much nicer as a post-apocalyptic hellscape instead of as a peaceful advanced society. Then he decides Malthusian philosophy is pretty awesome, despite the fact that Dr. Malthus would not be born for a few thousand years.
Odin places the Tessaract, containing the space stone, in the keeping of a house of peaceful monks. This can’t possibly go wrong.
An ancient mage, god, or extradimensional being, forges a necklace to hold the time stone and calls it the Eye of Agamoto, because Deus ex Machina was not yet a concept.
The Kree Supreme Intelligence, a biomorphic computer composed of the uploaded mental engrams of all the greatest Kree, starts using telepathic dreamscapes to communicate because it doesn’t want anyone to know it really looks like Krang from the Teenage Mutant Ninja Turtles TV series.