A brief explanation on origins of Celestials in marvel Multiverse

This one eyed creature is called THE FIRST FIRMAMENT.

Many eons ago, it was the very first Eternity.

It was all there was in existence, and became lonely.

So it created the Aspirants. Some dark in appearance, while others were multi-colored.

The Aspirants worshipped the First Firmament, which pleased him (it).

However, the multi-colored Aspirants rebelled against their darker brother’s.

War broke out, tearing the Firmament into pieces. Most of the pieces held together and fled. The torn pieces formed another Eternity, in the void that the Firmament left behind.

Time passed, and many Eternities formed.

The multicolored Aspirants won their war over the dark ones, and with each new Eternity, it would subconsciously continue to create the multicolored Aspirants.

The multi-colored Aspirants became the Celestials, the dark ones were now called Dark Celestials.

Inside Eternity, the Celestials were given purpose, creating life on different planets, shaping the Universe, which pleased Eternity.

Many years passed, and the mystery of who, and what these 2000 ft tall iron men were, grew.

What was also a mystery, were their births, each one being created in a different manner.

All to serve the Fulcrum.

Which was the sentient of Eternity.

Their interaction with earths heroes and their allies grew as well.

Their history throughout Marvel is massive, it would be impossible to list it all here.

The Celestial’s arrive on different planets, and restructure them, to either support life, or be destroyed.

Each Celestial has its own power level and purpose.

There are literally thousands of Celestials, but the most powerful among them were…

TIAMUT THE DREAMING CELESTIAL

It could be argued that Tiamut was the most powerful member.

Later in his history, he evolved, and became one with Eternity ( the Fulcrum ).

Some have said the being in blue was God, that Tiamat became one with the creator.

ARISHEM THE JUDGE

His purpose was to judge the worthy and unworthy, inside his thumb was the formula to life and death for entire planets. He was usually the leader.

EXITAR THE EXTERMINATOR

Massive in size, he could destroy an entire planet with one blast.

SCATHAN THE APPROVER

Little is known about Scathan, but it is assumed his power level was among the greatest, if not the greatest.

THE ONE ABOVE ALL

Called “the one above all”, because he was in charge of his group of Celestials.

Because their purpose was beyond human comprehension, some were often misunderstood, while others, had sinister intentions, this included some alternative universe Celestials, or Celestials from a different time period.

Against Thanos with the infinity gauntlet, their intentions were good.

As well as helping against the Many Angled Ones

Tiamut for instance, was betrayed by his fellow Celestial’s, and sought revenge on several occasions, by attempting to conquer the universe himself.

His attempts were stopped by earths heroes, and Galactus.

Although their power is immense, they can be killed.

There are so many Celestials, that collectively, they are one of the most destructive force’s in existence.

There appearance’s in the MCU has been limited.

Hopefully we'll see more of them in the future.

In the comics, Ego was NOT a Celestial, he was an Elder of the Universe, in the MCU, he is a Celestial, and so was Star-lord, ( which was ridiculous ).