The first trailer for The Eternals was revealed at the Marvel Studios panel at the Brazilian Comic-Con Experience 2019. While the video itself is not available for online streaming, IGN Brazil was there to break down what was shown.
The footage starts with a door opening. An old man says he “missed them” to the beings before him — the Eternals, with Ikaris (Richard Madden) out in front — and asks them to make themselves at home. The Eternals are wearing casual clothing rather than their costumes here.
We then see the heroes laying on the beach, the sky’s color indicating dusk is coming. It seems like they don’t know where they are. During the evening, the Eternals are gathered around a fireplace. Ajak (Salma Hayek) is the leader of the group.
Source: IGN.com Marvel's Eternals: Trailer Footage Description