Adventurer or "Hero" is the lore name for player characters. Although unnamed and numerous, it is thanks to these brave individuals that Azeroth has been saved on numerous occasions in recent (and past) times.
Races and classes
The adventurers mostly come from either of the two larger factions on Azeroth, being the Horde and Alliance (death knights are considered part of The Knights of the Ebon Blade though they mostly retain their allegiance to their former faction). As such, most of them are of the thirteen larger races of each faction, namely blood elves, darkspear trolls, draenei, dwarves, forsaken, goblins, gnomes, humans, night elves, orcs, pandaren, tauren and worgen.
Adventurers are mostly loyal to their faction, Horde or Alliance, but are willing to work for other neutral organizations such as the Argent Dawn or Steamwheedle Cartel for either gold or faction rewards. Adventurers remain very loyal to their home factions, however, and will quickly respond when they hear the call to a war.
The adventurers of the Horde and the Alliance usually cannot tolerate one another, and will often kill each other mercilessly at the slightest provocation, or for no reason at all. This behavior hasn't changed even since the onset of the Fourth War. Although, this seems to be based more on their ruthlessly competitive nature and less on any sort of racist philosophy. Adventurers frequently perform neutral tasks for members of the other faction's races - sometimes even the exact same tasks as their competitive brethren - and have shown no hesitation in fighting alongside their "rivals" against a common enemy. One of the most recent examples was during the assault on Icecrown Citadel: Alliance adventurers fought the Val'kyr champion Sister Svalna alongside the Orc Death Knight Crok Scourgebane on their way up the tower, and during the fight against the Lich King himself, Horde adventurers raised arms alongside the human leader of the Argent Crusade, Tirion Fordring.
Indeed, their animosity seems mostly directed towards other adventurers, though town guards are often collateral damage. In some cases, the opposing faction's auctioneers are frequently targets of a vengeful adventurer.
Where a regiment of orc grunts or human footmen fail, the adventurers succeed. Many are one-man armies, being able to defeat a large number of enemies, whilst even getting stronger. Their strength comes from slaying foes and performing tasks as well as from the magic coming from their armor, weapons or magic items. Yet, when the time comes, adventurers work together, unlocking incredible power to defeat powerful monsters and hated enemies that even entire armies could not triumph against. According to the Lich King (a victim of their power himself), the adventurers that slew him were the strongest fighting force of Azeroth, strong enough that he desired to make them his undead generals.
Although each adventurer has a different set of gear, all have a hearthstone, save for a few adventurers that mistreat or lose theirs. This magic stone, through some sort of strange, arcane ritual performed by an innkeeper, allows the wielder to return to a specific location where the stone is bound to.
Though uncertain why or how, the adventurers saved the day numerous times in recent years.
From fighting on the same battlefields as the Orcish Horde during the First and Second Wars, to assisting Prince Arthas Menethil in purging Stratholme and battling the Burning Legion atop Mount Hyjal.
Four years after the third war, the Adventurers found themselves overwhelmed with work, from stopping Orgrimmar's corruption from Ragefire Chasm and preventing the prison break in the Stormwind Stockades. They are responsible for ending the Defias Brotherhood's criminal Empire, by killing its leader in the Deadmines. Adventurers of the Horde have also been able to slay Zalazane and reclaim Echo Isles, whilst those of the Alliance were able to liberate Gnomeregan from the traitorous Mekgineer Thermaplugg.
Adventurers have aided the druids of Naralex to free him in the Wailing Caverns, destroyed the Scarlet Crusade's presence in the Scarlet Monastery. They investigated the ruins of Dire Maul and the sacred Maraudon. They contributed to ending the Scourge experiments in Scholomance and slaying the scourge in Stratholme, including Baron Rivendare and Balnazzar.
They also aided in the chaotic Blackrock Mountain, defeating Nefarian in his Lair halting his plans. On the other side of the world, they gained favor with the Brood of Nozdormu in Silithus, and are responsible for the re-opening of the Gates of Ahn'Qiraj. In the Plaguelands they joined the Argent Dawn in fighting off the Scourge during its invasions and sparking the invasion of Naxxramas. Despite the common word, some adventurers claim it was they, not Varian Wrynn, who have slain Onyxia. Some even claim they have slain her not once, but twice.
As of the Burning Crusade
This section concerns content exclusive to The Burning Crusade.
A year after these events, by the request of either the hunted Draenei or the betrayed Blood Elves, they journeyed into Outland, holding off the Illidari and disrupting Burning Legion activities. They have also aided in restoring the timeline in the Caverns of Time. With their aid, Lady Vashj, Kael'Thas Sunstrider, and Illidan Stormrage, powerful aggressors who resided in Outland, were defeated. They also prevented another large-scale invasion of Azeroth by the Burning Legion when they fought alongside the Shattered Sun Offensive to subdue Kil'jaeden and restore the Sunwell.
Against the Wrath of the Lich King
This section concerns content exclusive to Wrath of the Lich King.
Another year later, Death Knights, having revolted against their master, joined alongside the adventurers to the fight against the evils of the Undead Scourge in Northrend, ending the Nexus War, and driving back the Old God Yogg-Saron with the help of Brann Bronzebeard and the Kirin Tor. They braved the Argent Tournament, even going as far as assaulting Icecrown Citadel and defeating the Lich King alongside Tirion Fordring and the Ashen Verdict. They also made great strides ingratiating the mortal races to the Dragonflights, helping prevent the remains of their ancestor Galakrond from Scourge corruption, slaying the corrupted and insane Malygos, stopping the creation of Twilight Dragons in the Obsidian Sanctum, and expelling the cruel Black Dragonflight (and their commander, Halion), from the Ruby Sanctum. Alexstrasza and the other aspects owed them a great deal.
Surviving the Cataclysm
This section concerns content exclusive to Cataclysm.
Three years after the Lich King's fall, the adventurers were called upon once again. The chaos brought about by changes in leadership, the fourth war and mass panic due to the cataclysm placed a great burden on the adventurers. The Goblins of Kezan, forced from their homes, bolstered the forces of the Horde. While the secluded Gilneans, transformed into Worgen, rejoined the Alliance for assistance in the face of the Forsaken invasion. Malfurion Stormrage had called upon many to assist him in the defense of Mount Hyjal once again from Ragnaros' armies and the Twilight's Hammer clan. They have brought trust back between Therazane and the mortal races, and ended the Naga plot to usurp Neptulon, earning his allegiance. In the hidden desert of Uldum, the adventurers dealt a crushing blow against Deathwing by defeating Al'Akir and his armies. After slaying the restored Nefarian, they took a more active role against Cho'gall and the leaders of the Twilight's Hammer. The adventurers aided Vol'jin in battling the resurfaced Zandalari tribe of trolls, who had reentered Zul'aman and Zul'gurub and used them as bases of operations. Following that, the adventurers were called back to Mount Hyjal, to aid in stopping Ragnaros's reinvigorated attack, as well as helping Thrall, who had had his spirit broken into four pieces by the new Majordomo Staghelm of the firelord's army. After rescuing Thrall and halting Ragnaros' attack on the world tree, they entered the Firelands, struck down Ragnaros' most powerful lieutenants, and finally, slew the Firelord himself.
With the help of the Bronze Dragonflight, the Adventurers retrieved the Dragon Soul that Malfurion Stormrage hid long ago at the Well of Eternity before its collapse. After escorting Thrall to Wyrmrest Temple and exposing Archbishop Bendictus, the Adventurers held out against Deathwing's relentless assault to retrieve the Dragon Soul. After the first attempt to destroy Deathwing failed, the adventurers parachuted onto his back and removed his protective armor. The Dragon Soul sent him falling into the Maelstrom. Deathwing arose and after one last battle, he was struck a third time with the once again empowered Dragon Soul and vanquished him once and for all. The aspects lay exhausted and powerless, as Alexstrasza heralded the beginning of the age of mortals.
Parting the Mists of Pandaria
This section concerns content exclusive to Mists of Pandaria.
After an intense battle between the Alliance and Horde fleets in the South Seas, they stumbled upon the previously-shrouded continent of Pandaria. Both factions battled each other for dominance as they explored Pandaria and forged alliances with its native races.
Adventurers assumed a pivotal role in the initial exploration of Pandaria, having been sent there by their respective faction leaders. The Pandaren chose sides, with some choosing to side with the Alliance, and some with the Horde. The conflict between The Alliance and Horde on Pandaria awakened ancient, evil manifestations representing the emotions of Doubt, Despair, Violence, Anger, Hatred, Fear across the continent. Adventurers fought against these beings and their negative effects on Pandaria throughout the campaign, eventually defeating them.
The Mogu began rebuilding their empire on Pandaria in an attempt to retake the continent they once ruled. Adventurers were forced to venture into the Throne of Thunder where they defeated the Mogu demigod known as the Thunder King and eliminated any chance of the Mogu ever regaining power in Pandaria.
After taking leadership of the Horde, Garrosh Hellscream became obsessed with discovering the secrets of Pandaria and using them as a weapon against any who would oppose him. Garrosh's reckless quest for dominance of Pandaria (and Azeroth) and his corruption by the Sha of Pride caused the horde to splinter. The Horde still loyal to Garrosh was identified as a threat by both the Alliance and Horde, who joined forces during the Siege of Orgrimmar. Adventurers accompanied various faction leaders during the assault, fighting their way into the heart of Orgrimmar and defeating Garrosh.
Confronting the Warlords of Draenor
This section concerns content exclusive to Warlords of Draenor.
When Garrosh's escape back in time prompted a new invasion by the Iron Horde through Azeroth's Dark Portal, Adventurers were called upon to fight back the attackers in the Blasted lands. Once the initial attack had been thwarted, adventurers joined a small, but powerful vanguard of both Alliance and Horde forces through the Dark Portal to shut it down from the other side.
In recognition for their previous service to the Alliance/Horde, having proven themselves countless times over the years, Varian Wrynn/Vol'jin appointed them as Commander of the Alliance/Horde expedition on Draenor. Throughout the events on Draenor, adventurers were therefore referred to as "Commander" by most Alliance/Horde-affiliates. When adventurers progressed well into their campaign on Draenor, fully fortifying their Garrison and amassing a formidable Alliance/Horde force, Varian/Vol'jin himself refers to them as "General".
At some point, adventurers witnessed the defeat of Garrosh by Thrall in Nagrand, who called on the forces of nature in Draenor to help defeat him. However, this did not end the threat of the Iron Horde, as adventurers discover Gul'dan had taken over from Grommash after a mysterious encounter. Khadgar, who has been chasing Gul'dan throughout Draenor, convinced adventurers to join his pursuit of Gul'dan to his new base of Hellfire Citadel.
Banishing the Legion
This section concerns content exclusive to Legion.
After Gul'dan escapes to Azeroth on a mission for his demon masters and opens the Tomb of Sargeras, allowing the burning legion to invade Azeroth once more, the adventurers fight alongside champions of the alliance and horde at the Battle on the Broken Shore. At the broken shore, the adventurers witness the death of Highlord Tirion Fordring and King Varian Wrynn, while horde adventurers witness the death of Warchief Vol'jin in Orgrimmar shortly after the battle.
With the return of the burning legion, the night elven wardens release the Demon hunters as a last resort to help in their fight against the burning legion. After escaping the vault of the wardens, demon hunters are greeted by Khadgar, who explains the situation with the burning legion and asks them to join the ranks of the alliance and horde.
After their defeat at the Broken Shore, adventurers head back to the Broken Isles to seek powerful artifacts called the Pillars of Creation based on direction from Azeroth itself, which will aid them against the Burning Legion. As part of their campaign, adventurers retrieve powerful artifact weapons such as Ashbringer and Doomhammer.