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human
[Thor 2 / MCU] what were the dark elves up to for first 13 billion years, and/or what 'light' did they hate?

So if I assume the Dark Elves are literally trying to extinguish the stars of the nine realms, and stars formed within about 200 million years of the universe, what were they doing for the majority of time?

Odin said the Dark Elves predate the dawn of the 9 realms: 

>ODIN: There are relics that predate the universe itself. What lies within her appears to be one of them. The Nine Realms are not eternal. They had a dawn, as they will have a dusk. But before that dawn the dark forces, the Dark Elves, reigned absolute and unchallenged.


And the big fight between Asguard and the Dark Elves was only 5000 years ago at the last convergence (the King of Asguard, Bor, Odin's father, faught at the battle, and Asguardian lifespans are 5000 years from a Loki quote):

>ODIN: We are not Gods. We are born, we live, we die. Just as humans do.

>LOKI: Give or take 5,000 years


So if they were hating stars undergoing fusion for 13 billion years so much, why hadnt they done anything about it until then? 

Why do they hate stars?  Is it just the literal light of the stars? Is it black-body radiation they rail against? 

If they were the dominant race from before the light, did they come from before the universe was born (before stellar-fusion there wasn't much more than hydrogen out there..)?
gpt
Probably developing their technology and brooding. It takes a ridiculous amount of time to create technology without a significantly advanced source of energy; we got it easy on Earth because everything came from the Sun. For example, coal consists old plants that used the Sun's rays and died and formed coal, while wind is caused by pressure differences created by the heat of the Sun, and so on. If you go back far enough, all energy sources on Earth originate from the Sun (and other stars, if you really wanna go back further). Difficult to jump-start technology if you barely have any sources of energy.

However, it must be pointed out that the Dark Elves ruled by default; they were the only sentient beings that existed in the first 13 billion years (save Celestials, who we can only assume didn't care about ruling the Universe). Technically, they ruled unchallenged and undefeated because **there was nobody to challenge them in the first place**.

The Dark Elves seem to have a pretty good tolerance to black-body radiation, but the problem lies in them not being able to stand what comes from it; other life and contenders. Once other life shows up, you can trace that lifeform's origin to its homeworld and the star that nourished it. If life is started by stars, and life ruins the Dark Elves' existence, then stars are bad. Simple logic right there, so the Elves decided to fix their issue.

Even then, we can only hope that Odin really liked telling overly exaggerated stories to make them more interesting. They might be obsessed with turning the universe into a barren dark void and advance entropy.


TL;DR: Dark elves don't like too much light and were dying out because of so many stars being born... so they decided to delay their extinction. They ruled by default because nobody else existed, and Odin may really like hyperboles.