In the monumentous scene where the story of the infinity stones are first and formally revealed to the audience, we have an anectode about a group that was once "able to share the [infinity stones'] energy amongst themselves", but only for a moment until they were consumed by that energy.
This seems like quite a telling MCU moment to be forgotten quite quickly by most. When watching this scene, the individuals are dressed in somewhat ceremonial garb that hides their appearance. Below those garbs, might we see some grotesque, near immortal creatures thought capable of harnessing the stone's power? When being consumed by the energy of the power stone, the individuals seem to flail in an unnatural way, without any limb movements. The faces seem to be obstructed with more covering and lack any facial expressions. They seem like lifeless puppets hidden under layers.
The Deviants are antagonists of The Eternals, and this scene may actually show The Deviants at work. Many of The Deviants are depicted as frightening creatures, often hidden under disguises of their own accord. Deviants are also early experiments of The Celestials. So this theory could all fit well.
Do you agree that we may have seen some of The Deviants and not known about it?