In the mid-credits scene, we hear from three Kang variants: Immortus, Rama-Tut, and … maybe a not-scarlet version of the Scarlet Centurion that appears to be somewhat robotic. He says that the exiled one is dead (meaning The Conqueror), though Rama-Tut asks if that’s a sure thing. They seem to believe it is, but that doesn’t mean it’s true. The discussion is about how they’re upset because they weren’t the ones that took him down. They mention that it was done by others, which seems to mean Scott and friends. Immortus then says they have begun to touch the multiverse and that, “if we let them, they will take everything we built. So let’s stop wasting time,” and we see a shot of the timeline streams from “Loki.” “They” likely means Scott and the rest of the Avengers of Earth-616. The centurion(?) asks how many were called, and Immortus says, “All of us.”
We see a huge stadium full of Kang variants. Identifying them would be like doing a Where’s Waldo hunt, but I saw a Skrull, a blue-skinned one, one with a cape, and one in a mask. They’re laughing maniacally and cheering.
It’s hard to explain all the Kang variants, but they all stem from Nathaniel Richards, born in the 30th century on Earth-6311. Earlier in that timeline, a time traveling-man with the same name from Earth-616 (the Avengers branch) appears, bringing peace to that future.
Later, a bored Nathaniel from Earth-6311 travels back to ancient Egypt on Earth-616 and rules as Pharaoh Rama-Tut. While trying to escape from the Fantastic Four, he ends up in modern Earth-616 and makes the Scarlet Centurion armor for himself. Immortus is the future version of Kang, who has fought against and alongside the Avengers at different points.