This season is focusing on the Eternals, featuring Arishem (the Celestial/big red guy).

I've never been super familiar with the characters, so if I remember the movie correctly, Arishem commanded the Eternals to watch over Earth until the planet had enough...lifeforce? to birth a new Celestial; the Eternals eventually fought each other over whether or not they would continue with that purpose, after coming to love humanity. This led to the big fingers sticking out of Earth, which never gets mentioned anywhere else in the MCU - a plot hole so big you could drive a Celestial through it!