Tempus is an agent of Immortus. He claims to have existed in his own dimension, a "chronal continuum," a "world existing outside the time we know but obviously paralleling our own," since the "beginning of eternity", unchanging. The ennui of his existence has given him a desire for his own death. Immortus, however, claims to have created Tempus himself, fashioning him from "the very ether of Limbo."

When first seen, Tempus manipulated Willie Lumpkin into entering the Baxter Building where time machine of Doctor Doom was being kept by the Fantastic Four. Willie was sent on a directionless journey to various points in time, causing time paradoxes as he went. Tempus hoped that the paradoxes would cause an end to the universe. (According to Marvel Two-In-One #50, time travel and the paradoxes resulting from it cause the creation of alternate realities. The idea was set by John Byrne and has since been the rule for Marvel's time travel stories. The retcon would mean that Tempus' plan would actually cause the existence of new realities.)

The Fantastic Four (Human Torch, Medusa taking the place of Invisible Woman, Mr. Fantastic, and the Thing) returned from space to find an Earth with vast differences than the one they had left. There were no cities in this Earth, only wilderness and the only humans were primitive hunters. Uatu the Watcher explained that history had been tampered with and sent the Four back in time to set things right. Reed and Johnny found themselves in the American Revolutionary War (1775–1783), having to rescue George Washington from British captivity. Willie had accidentally scared Washington's horse which threw the officer down. Washington had been unconscious when arrested. Ben and Medusa found themselves in 1928 Chicago having to rescue Willie from gangsters. Willie had been giving them stock market tips from the advantage point of four decades in their future. With both missions successful, the Four and Willie were transported to Tempus' dimension. He proved quite a match for any of the Four until Mr. Fantastic restrained him by wrapping his body around him allowing the Thing to trip Tempus and the impact shattering him. The five time-travelers safely returned to the Earth of their own time.^[2]

When Thor attempted to travel through time to investigate the history of the Celestials, he ended up in Immortus' Limbo where the Ruler of Limbo confiscated Mjolnir. Thor agreed to an alliance with the Space Phantom to get his hammer back. The two had to get past Tempus to reach Immortus. Tempus attacked the Asgardian with a club but Thor wrestled control of it. Thor proceeded in shattering Tempus' face.^[3]

Immortus had taken control of the Scarlet Witch. The West Coast Avengers (Hawkeye, Iron Man, Dr. Hank Pym, USAgent, Wasp, and Wonder Man), as well as Quicksilver, arrived to retrieve her but had to pass Tempus to do so. He picked Wonder Man as if he were a rag doll (according to Pym's description) and aged him to a very feeble old man. He then threw Simon to USAgent, knocking them both out. Pym's weapons, Hawkeye's blast arrows, and Iron Man's repulsor rays could not hurt Tempus, but Quicksilver got the idea of hitting Tempus with Limbo's own materials, managing to hurt the giant. Tempus returned the favor by having them relive their most painful memories. The Avengers were all reduced to quivering helplessness.

Immortus contemplated if he should have Tempus kill the captives or not, reluctant to confirm his status as a villain. Meanwhile, Agatha Harkness had entered Limbo unseen and managed to awaken the Scarlet Witch from a catatonic state. Scarlet Witch knocked everyone aside, rescuing the seven fallen Avengers, and confusing Immortus and Tempus. The Time-Keepers then arrived to punish Immortus for acting against their command and actually threatening their own existence instead of protecting it. Tempus wisely did not intervene.^[4] (According to a later retcon, these were not the Time Keepers at all but their counterparts and rivals the Time-Twisters).

Tempus's next appearance shows him leading an army of composed of Dire Wraiths, robots of Rama-Tut, and Space Phantoms. His master Immortus had siphoned reality-altering nexus power from four realities and had evolved into a quantum wave. He set about recreating the Multiverse. The Time Variance Authority opposed him and recruited four agents to go to Limbo and stop the process. They were Dr. Doom of Earth-772, Irondroid of Earth-90110, Thor of Earth-9260, and the vampire Wolverine of Earth-9250. They arrived in Limbo and encountered Tempus and his army. Tempus found he could not age either Thor (a god) or Wolverine (a vampire). The four agents were about to win when Immortus reset time back to the start of the battle, improving the strategy of his troops. The Dire Wraiths and the Space Phantoms respectively killed Doom and Irondroid, leaving only Thor and Wolverine. However. other agents of the Time Variance Authority had been sent to alter young Nathaniel Richards (the civilian identity of Kang and Immortus) preventing him from ever becoming a nexus being. With the conflict over, Immortus became human again and Tempus continued serving him.^[5]

Kang, a younger counterpart of Immortus, drained the life forces of the Council of Cross-Time Kangs (an organization including thousands of Kang counterparts and their successors from various realities) and used the energy to empower Tempus who grew to enormous proportions. Kang then send him against Alioth, an extra-temporal entity with ambitions of taking over space-time. Alioth tried using his temporal energies to defend himself. Tempus simply fed on them and kept on growing. The two opponents were locked in a stalemate which, according to Kang's plans, would last forever.^[1]

Immortus summoned Tempus, back to normal size and power levels, to use against Rick Jones. Tempus started draining the life force out of Jones, but Kang arrived and slashed Tempus to pieces. Kang and Immortus were locked in conflict at the time and Jones was an ally of Kang.^[6] Tempus was briefly seen by Immortus during his confrontation with Kang.^[7] Tempus later faced Hawkeye who used Pym Particle to grow to the size of a giant and strike him, which caused Tempus to fall over and shattered into pieces.^[8]

Tempus' last appearance was when Immortus summoned him to fight the Annihilators (Beat Ray Bill, Gladiator, Ikon, Quasar, Ronan the Accuser, and Silver Surfer) traveled to Wraithworld, which was located in Limbo, to investigate to save the Dire Wraiths on the barren world. Immortus had been using the Dire Wraiths as foot soldiers and tried to prevent the Annihilators from succeeding by sending out his Army of the Ages led by Tempus.^[9] During the fight, Quasar blew off one of Tempus' arms, though Quasar knew it would eventually grow back. However, when Quasar appealed to Immortus, Immortus realized Quasar's importance to future events. So, Immortus called off his forces including Tempus and allowed the Annihilators to pull Wraithworld out of Limbo.^[10] With Immortus' apparent death,^[11] Tempus' fate is uncertain.

• Superhuman Strength: Tempus possesses vast strength allowing to fight foes as strong as Thor. He can increase his strength by growing in size to the point where it exceeds 100 tons.^[12] At his maximum size he can hurt the likes of the Silver Surfer.^[13]
• Superhuman Durability: Tempus also possesses incredible durability. Attacks from multiple Avengers didn't faze him. Like his strength, his durability increases by growing in size.^[12]
• Superhuman Stamina: Being immortal, Immortus possesses almost limitless stamina if not limitless at all.^{[citation needed]}
• Time Manipulation: Tempus is able to manipulate time to make his enemies age upon touching them or blasting them with beams from his eyes. However, immortal beings like Thor are immune to this power.^[5] His enemies return to normal when he stops touching or blasting. Tempus can also create timestorms, which cause beings to relieve painful events in their lives.^[12]
  • Time Nexus: As a being made of temporal energies, Tempus could be used by Immortus as a means to transport large armies from across time to attack his enemies with.^[12]
• Regeneration: If Tempus is ever injured, he is able to recover from injuries at a fast rate. He can also regrow missing limbs. Due to his temporal nature, he can never truly be killed.^[12]
• Size Increase: Tempus can rapidly increase his size by absorbing temporal energy greatly increasing his strength and durability. By absorbing the temporal energies of dead members of the Council of Cross-Time Kangs, Tempus was able to grow from the size of a figurine to a giant in a short amount of time.^[14][12]
• Immortality: As a being made from temporal energy, Tempus can never truly die. If destroyed, Immortus can simply reform himself.
• Force Absorption: Tempus is seemingly able to absorb the force directed against him and direct it back at his attacker.

Tempus' power to absorb his enemies' force can be used against him by making him fall, which forces his own energy into him causing injury. This can even shatter him to pieces.^[2][8] While being made of temporal energy, he is also vulnerable to it.^[4] He is also susceptible to damage from his own warclub due to being made of the same temporal energies he is made of, as Thor demonstrated during one of their battles.^[15]

A giant warclub made from his temporal energies

As a being that lives in the time stream, Tempus doesn't have any alternate reality counterparts unlike many other Marvel characters. The Tempus seen in What If...? Vol 1 39 was the same one seen in every other appearance. This makes Tempus a unique multiversal being similar to the Living Tribunal.