Volstagg's History
Youth
Volstagg's origin beyond being a member of the Asgardian race and a friend of Thor has not been revealed. He first met Thor when the Warriors Three joined Thor's expedition to restore the Odinsword that had become cracked.
Volstagg was fairly advanced in age for an Asgardian, and it has been alluded to that he was a highly respected and feared warrior in his prime. He allegedly was named Volstagg the Staggeringly Perfect.
Allegedly, he led the youth Hogun the Good, Fandral the Quite Plain, Thor and Loki in Hel, fighting against all of its hordes for forty days and nights. Eventually Hogun was hurt and forced to retreat, Loki refusing to follow them. Volstagg was stabbed and Thor had to defeat the horde by himself, while Loki cared for the fallen warrior.
After this battle and eighty days without food, Volstagg started eating as soon as he could and never stopped since. This battle was allegedly the one that made Thor worthy of Mjolnir. Due to the battle, Hogun the Good became Hogun the Grim, and for some reason, Fandral the Quite Plain became Fandral the Dashing later.
Volstagg became a huge, bumbling oaf much given to boasting and bragging, the last into battle and the first to claim victory (usually undeserved). Referring to himself as the "Lion of Asgard," he usually caused more problems than he solved and seemed totally unaware of the chaos that almost always followed in his wake. A drunken Volstagg once incurred the wrath of Odin by spilling the secrets of the first Frost Giants to a younger Thor. Even so, he was considered a trusted and worthy comrade by his closest friends and allies, Fandral the Dashing, Hogun the Grim, and Thor.
Examples of Heroism
Despite usually being cowardly, Volstagg performed various acts of heroism. Volstagg once squared-off with the Hulk (before being dumped contemptuously in a roadside ditch by the green-skinned behemoth). The "Lion of Asgard" also once rushed through a tunnel to battle the demonic Mangog (a creature possessed of the power of a 'billion' beings) but was prevented when the passage proved too narrow to accommodate his considerable girth. Even more spectacular examples of his peerless bravery ensued: during a trip to Hades to rescue his comrade-in-arms Thor, Volstagg offered to battle the Arch-Fiend Mephisto in return for his friend's noble soul (despite being aware that the God of Thunder had already bested the Lord of Hell in fair combat some time previously).
Another example of Volstagg's bravery and heroism was when Thor and the Warriors Three were battling the interstellar parasite Ego-Prime in the streets of New York City: hiding behind a festering heap of garbage, Volstagg saw a group of extraterrestrial monstrosities preparing to devour a little girl, a sight which drove him to a remarkable display of courage and resolution. Despite his obvious terror, the Voluminous One struck the creatures down with his bare hands and carried the child to safety (it would be revealed much later that Volstagg was himself a family man and would never stand to see an innocent child harmed in any way).
When Balder the Brave returned broken and hopeless from the land of the dead, it was the kind-hearted Volstagg who took the fallen warrior under his wing (introducing him to the twin joys of gluttony and drunkenness).
When Thor's actions indirectly deprived two mortal lads (Kevin and Mick) of their mother, he took them to Asgard, and to the Hall of Volstagg, where he knew they would be loved and protected by the largest and kindest of all Odin's warriors. When the boys first mistook Volstagg for Santa Claus, he assured them that while he was not that particular time-honored saint, he was "yet a friend to children everywhere", as indeed he turned out to be.
When the Frost Giants descended upon a plague-ridden Asgard, Volstagg was the only warrior left to defend the ramparts, a role he fulfilled admirably, once he realized he had discovered an enemy even more stupid and cowardly than himself. Saving the day by default as always, the Lion of Asgard accepted the praise and gratitude of his companions with his usual humility, musing on how the poets of later ages will depict his glorious exploits for all time.
New Mutants
Volstagg and his family also encountered the New Mutants. During the group's first trip to Asgard, Volstagg made friends with Roberto Da Costa, aka Sunspot, challenging him to feats of strength, including arm-wrestling and the lifting of Volstagg himself.
In the group's second visit, Volstagg's children encountered Boom Boom, Hrimhari and Warlock, who were on the run from Hela's forces, who were following through with a plan to kill Odin and conquer Asgard. The children switched places with the group so as to impress their elders with the seriousness of the situation. They told the heroes of Tiwaz, a powerful sorcerer who might help them in the fight. Hrimhari, wolf-prince of a far-away tribe of wolf-people, told the children that tales of Volstagg's children were told to his people and it was an honor to be in their debt.
Volstagg later personally participated in the battle against Hela's forces, working with his Warriors Three comrades and other Asgardian forces; in the end Odin was saved.
Persecution
Soon after this point, when Odin was awake and aware, his mind became overtaken by the influence of Loki. Persecuted, the Warriors Three were forced to go on the run, gaining a new ally in the form of a heroic, young palace guardsman.
Clumsy Warrior
Volstagg seemed to know more about the raising of the mug (his favorite weapon, evidently) than the raising of the sword (of which he actually knew very little). Ironically, whenever his courage failed (at the slightest sign of danger), Volstagg's innate clumsiness would somehow seize victory from the jaws of defeat. In a typically Kirbyesque touch, Volstagg inadvertently saved his companions' lives on at least two occasions by stumbling onto the one weapon capable of saving the day (and later claiming that his initial cowardly retreat was all part of a vast master plan). It has also been hinted at on numerous occasions that he ceased his full time warrior's life to be a husband and father.
Ragnarok
Eventually, Loki brought about Ragnarok. Volstagg, alone of the Warriors Three, survived the initial attacks. He was later discovered by Thor taking refuge in a statue of Frigga and having lost considerable weight. He united with Thor and eventually fought in the final battle of Ragnarok. There, along with the rest of Asgard, he died.
As the other Asgardians, he returned, this time to Midgard, where a new version of Asgard had arisen in the Midwest of the United States.
Soldier Field and the Siege of Asgard
Volstagg was later set up by Norman Osborn and Loki, and inadvertently caused the deaths of thousands of American citizens when he accidentally destroyed the packed stadium of Soldier Field while fighting the U-Foes. This tragedy was used by Osborn to justify the fateful siege of Asgard which would culminate in its eventual destruction.
Fear Itself
When Odin planned to destroy the Earth to save the rest of the known worlds from the Fear Serpent, Volstagg was forced to be one of many to keep Thor under control. Odin soon changed his plans, leading an army to Midgard to slay the Serpent. The Warriors Three, at the forefront, were just in time to see the Serpent and Thor slay each other in battle.
War of Burning
When the ancient Fire Giant Surtur used the grudges the Vanaheim have against Asgard it inflamed a war that affected the Nine Realms. When Volstagg thought Loki was part of it, a suggestion to imprison the trickster led Thor to battle the Warriors Three. After the All-Mother lost their rulership of Asgard due to their connection to the Vanaheim, Volstagg became the new ruler. He led a war through much of the Nine Realms. He tried to give a pardon to the All-Mother, but they refused, saying the people's trust did not match Volstagg's. Later, Surtur's forces were defeated thanks to Loki and Volstagg stepped down to rule only over his family once again.
War Thor
Having become a senator of the Congress of Worlds Volstagg travelled to Nidavellir as part of a diplomatic mission concerning Light Elf refugees displaced from Alfheim due to Malekith's attacks. When the camp was attacked by forces from Muspelheim, Volstagg tried to ensure the safety of a group of children he found among the destruction caused by the attack. While making their way through the fiery warzone, Volstagg and the children were targeted by an explosion, of which only Volstagg emerged alive. Seeking retribution and a way to put an end to the war that ravaged the Ten Realms, Volstagg was called to the abandoned City of Asgard in the Asgard-realm by the Mjolnir of an alternate universe which laid unclaimed. Volstagg lifted the hammer, and obtained the power of Thor.
After Fire Demons from Muspelheim attacked Light Elf refugees in Nidavellir, Volstagg chose to take the fight to Muspelheim itself and battled its ruler the Fire Giant Sindr, the Queen of Cinders. He then brought down a torrential rainstorm to flood Muspelheim and wipe out its entire population. The new Thor Jane Foster was forced to step in to prevent Volstagg from committing genocide by transporting herself and Volstagg to the Yawning Void. An angry Volstagg fought Thor until their fight took them to Svartalfheim. Odinson then appeared and took Thor's place in the fight. After learning from Roz Solomon that Volstagg was War Thor, Thor reverted to her human form and used her friendship with Volstagg to successfully convinced him to end his rampage, let go of his rage, and give up being War Thor.
Volstagg returned to Asgardia where he was to receive treatment for mental effects the Mjolnir had on him when the hammer unexpectedly appeared. Volstagg became drawn to the hammer and walked over to it while his friends futilely tried to stop him from reclaiming it. When Volstagg lifted the hammer, he once again became the War Thor and flew off. Even while clutching the hammer, Volstagg was conflicted on whether to continue being the War Thor. While in the Asgard-realm, he was ambushed by Odinson's goat Toothgnasher who Odinson put in charge of guarding the hammer. Volstagg prepared to battle Toothgnasher when a giant hand suddenly appeared and grabbed Toothgnasher before killing him. The hand belonged to the monster Mangog who had somehow returned to life to wipe out the Asgardians. Volstagg fearlessly charged at Mangog to prevent this from happening.
However, Volstagg was no match for Mangog and was brutally beaten down before having his Mjolnir destroyed. Mangog then punched Volstagg toward the edge of Old Asgard. Mangog demanded that Volstagg tell him where the Asgardians were. Volstagg vehemently refused. Before Mangog could finish Volstagg off, Malekith appeared and informed Mangog of the location of the Asgardians, the city of Asgardia. After Mangog left for Asgardia, Malekith stabbed Volstagg's hand with a dagger so he could fall to his doom. Volstagg's unconscious body was found in time and taken back to Asgardia where he was treated for the extensive injuries inflicted by Mangog, though he remained in a comatose state.
When Asgardia was destroyed, the Asgardians moved to the Bronx, taking Volstagg's unresponsive body with them. Volstagg regained consciousness by the time Malekith's War of the Realms reached Midgard, helping the counteroffensive against the Dark Elf and his allies by piloting the Destroyer since he was still physically incapacitated.