Little is know of how the Heroes first met or why they declared war against the second Overlord, though it can be assumed that they honestly wanted to end his tyrannical reign over the land - or, in the case of the more cynical members of the group, simply steal his treasures. One way or another, they united under the leadership of the Wizard and set out to liberate the land.
At some point during their quest, they were joined by an Eighth member; though his name and reasons for joining them remain unrecorded, this Eighth Hero proved instrumental in helping them defeat the Overlord. During the final battle, the Eighth Hero sacrificed his life in order to end the menace once and for all, grabbing the tyrant and jumping from the ramparts of the tower. Though the Overlord was killed instantly in the fall, the Eighth Hero was left mortally wounded at the bottom of the tower; though Oberon Greenhaze insisted on saving him - or at the very least, reclaiming his body - the rest of the group dismissed the notion. Abandoning the Hero to his fate, they looted as much as they could from the Overlord's treasures and fled the collapsing tower without a second thought for their fallen comrade.
The Seven then returned to their traditional homelands with much pomp and circumstance, immediately welcomed as the heroes of the land; many of them were crowned the rulers of their people, and many more were granted luxuries and privileges beyond their wildest dreams.
Unfortunately, the Seven had been corrupted from within: the second Overlord had escaped death by possessing the body of the Wizard, and now walked among his former enemies unseen, subtly encouraging them to indulge their basest desires. One by one, the Heroes slowly succumbed to their darker natures, each one becoming as bad a villain as the Overlord had once been: Melvin Underbelly's gluttony and Goldo Golderson's greed led them to build whole empires dedicated to feeding their bottomless appetites. Jewel's envy drove her to steal from her friends and her supporters time and again - even though she had no real interest in the burgled items once she had them. Oberon's sloth not only allowed Goldo to enslave his people, but also led to him merging with a magical tree, allowing his nightmares to attain physical reality and infest the forest. Sir William gave into his lust, not only cheating on his fiancee Velvet, but also forming a pleasure cult devoted to summoning a succubus - one that eventually led to the zombie plague infesting Heaven's Peak. And, of course, Kahn gave into his wrath, leading his barbarian hordes on raids against peaceful settlements throughout the land, destroying everything in sight.
The Events Of The Game
Several years later, the Eighth Hero is resurrected as the Third Overlord by Gnarl and the Minions; at the time, he is led to believe that he is actually the original Overlord defeated by the Seven Heroes so long ago. As such, he sets out to take revenge on his killers, reclaim the treasures they stole, and reunite the Minion clans who once served him - hence the events of the game.
Unknown to both the character and the player, this "revenge" is really just another one of the Second Overlord's schemes: having grown tired of posing as the Wizard and watching the corrupted heroes rampaging across the countryside, he has decided a return to the status quo is necessary. He ordered Gnarl to resurrect the Eighth Hero and sculpt him into the perfect means of killing the ex-heroes and reclaiming the property they stole from him.
However, the Wizard does not show himself until the Third Overlord has managed to slay five of the heroes and imprison Jewel for good measure. Only then, with his tower restored and all his property reclaimed, does the Second Overlord appear, seizing control of the minions and reclaiming the powers that the Third Overlord had acquired. However, with the aid of one of the Wizard's daughters (either Velvet or Rose, depending on which of them the player chose to favor), the Third Overlord was able to reclaim a small number of minions and challenge his predecessor to one final battle - which he won, ending the threat of the Wizard and dissolving the Seven Heroes for good.
In the expansion pack Raising Hell, the fate of the heroes is further elaborated upon when the Overlord travels into the Internal Abyss; here, the deceased members of the Seven Heroes are being punished for their sins by a deity known as the Forgotten God. Though the Overlord was eventually able to defeat him, he was trapped in the abyss by his treacherous jester - and quickly declared the new king by the wraith inhabitants.
Officially, this was the last time the Seven Heroes appeared on screen, with Jewel's fate remaining unknown. However, in the event that she didn't die in captivity or escape at some point between the two games, it is possible that she was killed when the Tower Heart exploded in the backstory to Overlord 2.
Though the Seven Heroes were permanently dissolved, their legacy remains in the form of the Third Overlord's legacy: having won the heart of the Wizard's daughter Rose (canonically established by the sequel), he chooses her as his mistress. Some time after the Overlord is trapped in the Infernal Abyss, Rose gives birth to his son - later known as the Fourth Overlord, or Overlad, in the sequel.
- The Wizard, leader of the group - later revealed to be the second Overlord possessing his body.
- Melvin Underbelly, a gluttonous halfling responsible for enslaving most of the Mellow Hills to feed his appetites.
- Sir William, a perverted paladin who betrayed his fiancee and led a pleasure cult in summoning a succubus.
- Oberon Greenhaze, an elf whose sloth led to the enslavement of his people and his fusion with a magical tree.
- King Goldo, an avaricious dwarf who enslaved the entire elven race to work his mines or serve as his consorts.
- Jewel the Thief, a human woman who betrayed and stole from her ex-comrades out of envy.
- Kahn the Warrior, Jewel's lover, renowned for fits of temper known to leave entire settlements in ruin.
- The 8th hero, later known as the third Overlord and son-in-law of the Wizard.
- The Seven are quite clearly modeled on the Seven Deadly Sins - Melvin representing gluttony, William representing lust, and so on. The Pride representative doesn't reveal himself until the end of the game in the form of the Wizard - both a victim and an inducer of pride: not only does he successfully trick the Eighth Hero into believing that he's the Overlord that so many people once feared, but he also spends much of the ensuing boss battle gloating over his cleverness in getting the heroes to succumb to their vices.
- The Seven are also dark parodies of common playable characters in fantasy roleplaying games: the thief, the paladin, the warrior, the wizard and so on. However, the Seven also draw influence from the Fellowship of the Ring in Lord Of The Rings - in itself an overwhelmingly popular influence for fantasy roleplaying games: appropriately enough, the Second Overlord (Overlords already resembling the depiction of Sauron in Peter Jackson's film trilogy, complete with plate armor and spiked helmet) has managed to cheat death by keeping part of his spirit kept out of harm's way.