Spoiler Warning for Disney+'s Loki
Alioth guards The Void for He Who Remains in Loki, and it is terrifying creature that consumes everything it encounters. Alioth is actually based on a character from Marvel Comics, and he's only one of several major temporal beings from the comics that have been represented in the Disney+ series.
There are many layers to the multiverse within Marvel Comics, including a temporal domain that is fiercely contested over by several characters, including one of the all-time best time travelers in comics, Kang The Conqueror. Some of the most powerful beings in the Marvel Universe rule over time and the door is open to them now in the MCU.
Alioth serves He Who Remains in Loki, and is essentially the guard dog of The Void. Their relationship is much different in the comics.
Alioth remains a giant purple cloud of energy and rules a temporal empire all his own. This empire borders that of Kang The Conqueror, a character many fans suspect is a variant of He Who Remains in the MCU. In the comics, Kang traps Alioth behind a massive barrier in time - something like The Void - and forces him into battle with another time being, Tempus.
Tempus is a cosmic being who Kang set against Alioth in The Terminatrix Objective, one of the best Kang The Conqueror comic story arcs. He originally appeared in Giant-Size Fantastic Four #2 back in August 1974. He has fought Thor as well, using his giant crystalline mace to bat around the God Of Thunder pretty handily.
Immortus hails from Limbo, a dimension that is currently ruled by Magik, Illyana Rasputin of the New Mutants. He's traditionally a servant of Immortus, who is one of the most powerful variants of Kang The Conqueror in the comics.
The Time Keepers play a major role in Loki. Though they're revealed to be mere figureheads in the MCU, they are powerful actors in Marvel Comics.
The Time Keepers were created by He Who Remains to protect time, essentially from themselves. His first attempt at creating guardians of time resulted in the Time Twisters. These beings went through time basically tearing it to shreds, leaving the Time Keepers to come behind them and try to set things right.
He Who Remains is very different in the comics than in Loki. This nameless figure hails from a prior universe and was the head of the Time Variance Authority that existed there. He was tasked with recreating the temporal watchdogs in the Marvel Universe.
He first appeared in Thor #245 and it was Thor's intervention that alerted He Who Remains to the destructive activities of the Time Twisters. To offset them, he created the Time Keepers.
Comic fans know the Time Variance Authority is essentially the time police of the Marvel Universe. They also first appeared in Thor, in issue #372 in 1986. They basically prevent anyone from changing the past or the future, though it's nowhere near as dogmatic as in Loki.
Still, they're very committed to the cause, and that sometimes results in nasty consequences. They put She-Hulk on trial in the early 2000s for revealing to a past variant of Hawkeye that his future self was going to die at the hands of the Scarlet Witch.
Revelation is a variant of Ravonna Renslayer in the comic books. Unlike the main Ravonna, who was abandoned by Kang and then sought revenge against him, Revelation married Kang and eventually succeeded him in his time kingdom. She became one of the most powerful temporal beings as a result.
She was in near-constant war with Alioth and other competitors in the temporal realm. Comic book fans know that Ravonna Renslayer could eventually spawn Revelation or other variants in the MCU.
Kronos was once the ruler of the Eternals on Earth and ascended to become a being with power over all of time. One of his scientific experiments failed, destroying his body but elevating him to a god-like status.
Kronos is actually the grandfather of Thanos, who would go on to snap away half of all life in the universe. Kronos didn't intervene in the battle over the Infinity Stones in the comics, but he nonetheless is one of the most powerful cosmic beings in the Marvel Universe.
Perhaps even more powerful than Kronos is the In-Betweener. This cosmic entity embodies every aspect of existence at once, including all of its inherent dichotomies. He exists beyond time and all throughout it at once, and frequently encounters beings who can travel through time like Doctor Strange.
He first appeared in Warlock #9 in 1975 and serves two even greater cosmic beings, Order and Chaos. Like him, they're mostly representations of concepts without real definition beyond what is seen.
Eternity is the living embodiment of the eternal in Marvel Comics and arguably the most powerful cosmic entity of them all. Eternity is the multiverse, as much as he is a person. Everything contained in the infinite timelines and realities of the comic books exists within Eternity, and the same is likely for the MCU.
This means that the very abstract-looking character will probably make an appearance in the MCU at some point, perhaps even in Loki season two, if the multiverse is explored further.
The Time Variance Authority police time. The Living Tribunal judges it. This cosmic entity presides over the entire multiverse and holds all other cosmic beings in check, essentially preventing any one of them from reshaping reality as they see fit.
The Living Tribunal is a strange creature that has a head with three faces that floats over his body. All three faces have to agree to a verdict for it to be binding. One of the Easter eggs in Loki episode 5 was a statue of the head of the Living Tribunal in the Void.
