In his first appearance, Heimdall warned Odin of a Vanna's reconnaissance of Asgard. When next seen, he battled Thor to prevent him from entering Asgard; He then battled Thor to prevent him from leaving Asgard. Heimdall was then immobilized by Seidring. Some time later, he encountered the Recorder.
Later still, Heimdall battled Thor at Loki's command. In the prophesy of Ragnarok, he severed the Rainbow Bridge, and sounded Gjallarhorn. He traveled to Earth with Kamorr the dwarf to search for human candidates for godhood. He gathered three such human beings, and arranged for them to be exposed to Ego-Prime's energies and become the first three Young Gods. Heimdall then accompanied the Asgardians into the Dark Nebula.
Heimdall later became afflicted by lethargy in one of Odin's absences from Asgard. He then blew Gjallarhorn to summon Odin's elite guard. Some time later, he summoned Asgardian troops to restrain Thor. Later, he battled Thor again to prevent him from bringing mortals into Asgard.
When Asgard was invaded by the fire demon Surtur, Heimdall attempted to defend the gates, but was overcome, and the Rainbow Bridge was shattered. No longer needing to be stationary, Heimdall spent more time in Asgard. Heimdall is given the Great Scepter of Odin to guard by Loki. Heimdall discovered Malekith's escape. He fetched Amora the Enchantress to help free Thor from ensorcelment. Heimdall later learned of Loki's possession of Surtur's sword.
Heimdall became close to Amora, who was soon infatuated with him. He comforted Amora about the Executioner's death. Heimdall rescued Balder from Seth's assassins. Heimdall was gravely injured during the war with Seth, the Egyptian god of death, when he was struck down in battle with the legions of Seth. Heimdall later battled Sif. Leir, and Caber. Heimdall confronted Surtur disguised as Odin about the imprisoned Grand Vizier. Heimdall led the legions of Asgard into battle against Ymir.
When Odin returned to Asgard after Surtur's defeat, he gave a portion of his power to Heimdall to restore the Rainbow Bridge, and Heimdall resumed his duties.
Around this time, Jason, a powerful member of the earth-based team the Pantheon, claims to have eluded Heimdall's senses during a trip through Asgard and over the Rainbow Bridge. Not many people trust Jason.
An alternate reality version of Asgard featured the realm itself floating over the East Coast of America. This raises worship of Thor, who was the ruler and he utilities Heimdall's senses to hear the prayers directed to him.
Asgard is struck by another Ragnarok, one from which there was no seeming reversal. Heimdall perishes in battle defending his people. Many Asgardians, Heimdall included, reform as Earthly beings.
Thor traveled to New Orleans to start his journey of finding the missing gods. After a confrontation with Iron Man, he encounters a man named Ezra, keeping vigil over a bridge. Realizing who he really is, Thor releases Heimdall from within the mortal. Heimdall was drawn to Ezra due to them both feeling angry and helpless due to the fact that neither of them could stop the destruction of their cities, New Orleans during Hurricane Katrina and Asgard during Ragnarok. Heimdall has now joined Thor in the new Asgard.
Heimdall also briefly possessed the Odinpower which granted him the ability to channel vast magical energies.
Heimdall is an experienced warrior and a fierce hand-to-hand combatant. He has proficiency with edged weapons and wields a variety of swords, shields and spears and, not surprisingly, he wears a suit of armor. Heimdall bore the Gjallerhorn, which he would sound to alert all of Asgard to dangers threatening the city's gates. While in the mortal form of Donald Velez he wore enchanted glasses which granted him super-enhanced vision.