Eson the Searcher is a flashback antagonist in the 2014 Marvel film Guardians of the Galaxy. He is a giant Celestial who is known for destroying a planet with the usage of an Infinity Stone.
When the Guardians paid a visit to the Collector by delivering the Orb (containing the Power Stone), the Collector explains to the Guardians about the origin of the Infinity Stones. To further prove the point, the Collector shows a footage of Eson the Searcher, explaining that the giant Celestial found the Power Stone and placed it in his staff for his own ambitions of conquest. Eson would later use the power of the Stone to destroy an entire planet civilization to satisfy his own ambitions of taking over the planet.
Despite succeeding in taking over the planet for himself, Eson would later lose the Power Stone to several cosmic beings, who later died trying to harness its power. This left the Stone to be hidden in the planet Morag where Star-Lord found it after evading several Sakaaran mercenaries sent by Ronan the Accuser, who intends to use the Stone to destroy the planet Xandar.
It's unknown what happened to Eson afterwards as the story took place thousands of years ago before the events.
Eson is one of the two characters in the film series to be a Celestial (the other one is Ego, who is revealed to be Star-Lord's biological father in Guardians of the Galaxy Vol. 2).
Interestingly, Eson has the usual appearance of a Celestial while Ego was not. It is unknown if other Celestials share Eson's or Ego's appearance or if Celestials in the MCU all have unique appearances.