World of Warcraft continues to challenge players with new expansions, content, and difficult end-game raid bosses. Beating the bosses of those max-level raids continues to be one of the most challenging parts of the game and is always intended to be difficult, for even the top-rated guilds with the best gear and best players.

In World of Warcraft's long history, there have been several near-unbeatable raid bosses that only fell after several hundred attempts. Not every guild kept track of how many attempts were made on these bosses in the earliest days, but in later expansions, tallying attempts were great for bragging rights.

Updated on December 31, 2023 by Kristy Ambrose: Blizzard continues to release upgrades and expansions for both the retail and Classic versions of the game, and sometimes that means a nerf for a previously impossible boss or the introduction of yet another equally challenging one. The choice of servers now includes Classic, Hardcore, Season of Discovery, Wrath of the Lich King, and retail, with news of a Cataclysm version on the horizon. The bosses of World of Warcraft are a creative mix of gods, ancient monsters, and legendary titans, all capable of bringing down the most coordinated and experienced guilds with complicated mechanics and powerful abilities.

16 M'uru, Sunwell Plateau

Numerous Attempts Among Five Guilds

• Expansion: The Burning Crusade

There's a lot of history behind M'uru, one of the toughest raid bosses in WoW. This otherworldly entity is also a formidable power in the lore for those who were paying attention during their first tour of Shattrath. It took five guilds several tries to down him back during The Burning Crusade, with SK Gaming getting the world first after a nine-hour fight. The number of attempts they made before succeeding has been lost to time.

What made the fight with M'uru so difficult was its Phase 2 form, when it changed form into a much smaller target and spawned a small army of void walker adds. The only way to avoid this was to kill M'uru before he had a chance to enter the second phase and the amount of hit points it had made this nearly impossible.

15 Lich King, Icecrown Citadel

More Than 170 Attempts

• Expansion: Wrath of the Lich King

Back in 2009, the Lich King was one of World of Warcraft's most notorious villains. The prince formerly known as Arthas had been a key player in the lore of the real-time strategy games and was one of the playable heroes in The Frozen Throne expansion of the classic 1990s games, so he would have to be one of WoW's hardest raid bosses.

Once The Wrath of the Lich King expansion was released for the MMO version of Warcraft, Arthas appeared again, this time as the Lich King himself in one of the new endgame raids. He hit like a truck and cast a damage-over-time spell that killed players with less than 90% health. Paragon was the guild that got the world first back then after about 170 tries, and now that he's been nerfed more people can enjoy the cinematic that was more than two decades in coming.

14 Onyxia, Onyxia's Lair

Undefeated For 69 Days

• Expansion: Classic

Just to clarify, this is the 40-player raid from the old days, not any of the several modern interpretations in the Wrath of the Lich King or retail versions. The closest equivalent would be today's Hardcore servers, so any player who stands in the fire isn't getting back up again.

Exactly how many attempts there were on Onyxia back in 2004 is unknown, but she was undefeated for 69 days until the US-based guild, Ruined, successfully defeated her. Onyxia was there in the very beginning, is a part of Azerothian history on both the Horde and Alliance side and was one of MMO history's first raid bosses.

13 Nefarian, Blackwing Lair

Undefeated For 77 Days

• Expansion: Classic

Blackwing Lair was launched with patch 1.6. It didn't take long for the entire raid to earn a notorious reputation for difficulty, and the end boss, a black dragon named Nefarian, was its savage climax. Aside from some bugs that made the first couple of bosses a road block, Blackwing Lair as a raid was a significant jump in difficulty compared to Molten Core or Onyxia's Lair.

At the end of the raid was Nefarian. Fighting this boss successfully took a lot of planning, timing, and just dumb luck. That's partly why he reigned supreme at the very top of Blackrock Mountain for almost three months before meeting his defeat.

12 C'Thun

Undefeated For 113 Days

• Expansion: Classic

The end boss of the raid that was the crowning glory of the Classic era, C'Thun wasn't just a big tough monster. The writers and designers of WoW had delved into the lore and brought an Old God into Azeroth as a special challenge for players to defeat. The fight was certainly difficult, but it was made even harder by some bugs that made the fight even more difficult than Blizzard intended.

The exact number of attempts on this unique and terrifying boss is unknown, but it lasted almost four months before it was defeated by Nihilum, a European guild on April 25th, 2006. There are a lot of tough boss fights in both the Ruins and Temple of Ahn'Qiraj, and the battle against C'Thun is one of the worst here, let alone one of the toughest in WoW history.

11 Blackhand, Blackrock Foundry

325 Attempts

• Expansion: Warlords of Draenor

Blackhand was the final boss of Blackrock Foundry in the Warlords of Draenor expansion. Blackhand's first phase usually went easy enough, with a few distractions thrown at players with the Marked for Death debuff for example. When Blackhand fell to 70% health, his second phase would begin along with a transitionary explosion, and then every 50 seconds he would summon a Siegemaker to the fight.

It was a raid that required intense communication and focus, as well as knowing exactly what to do at any given moment. It's no wonder it took 700 attempts for the world's second Blackhand kill.

10 Jaina Proudmoore, Battle for Dazar'Alor

346 Attempts

• Expansion: Battle for Azeroth

Jaine Proudmoore was a boss in Battle for Azeroth's raid Battle of Dazar'Alor. Her fight was not particularly difficult for any laundry list of reasons like Blackhand, but rather because of one mechanic unique to Jaina, a debuff called Chilling Touch.

Chilling Touch slowed players by 2%, stacked, and when it reached full stacks froze the player solid. One guild went to the extreme measure of changing the race of every member of the raid to troll because Trolls have a racial passive ability that reduces movement-impairing effects.

9 Halondrus, Sepulcher of the First Ones

357 Attempts

• Expansion: Shadowlands

This unique boss is entirely a machine. It's certainly not the first time that players have seen a boss of this nature before, but Halondrus was an epic fight for the ages. It was introduced in the Shadowlands expansion, and Liquid was the guild that made the first kill after more than 350 tries.

The crab form of Halondrus means it can move in any direction, and its armor and hit point are ridiculously high because of course they are for this giant mecha. The real challenge was the sphere phase, which was the second of three different parts of this fight. If the floating spheres reached the boss, they could wipe the whole raid, and getting rid of them quickly enough put guild cooperation to the test.

8 Queen Azshara, The Eternal Palace

359 Attempts

• Expansion: Battle for Azeroth

Queen Azshara was a boss in Battle for Azeroth's The Eternal Palace raid. Queen Azshara was a legendary character in World of Warcraft going back to Cataclysm. Her raid was just as legendary for its unique raid mechanics, which made her the hardest boss in WoW at least for a while.

Most of her skills revolved around targeting players who were in her line of sight. A successful Azshara raid required constant movement and constant knowledge of what was around the player – for casters, this was nigh on impossible.

7 Fallen Avatar, The Tomb of Sargeras

453 Attempts

• Expansion: Legion

The Fallen Avatar is one of the few enemies listed here who was not the final boss of the raid. Blizzard usually puts the hardest bosses at the end of the raid for the progression incentives. As the second to last boss of The Tomb of Sargeras in Legion, the Fallen Avatar raid was full of random elements that made consistent progress on the boss extremely difficult.

One such ability was Dark Mark, a debuff with unlimited range that targeted three random raid members, dealt massive damage, and then launched them into the air. He also dealt an insane amount of damage in waves to players close by based on buffs the boss gained constantly. The only way to get a good run with the Fallen Avatar was to hope party members with low health didn't get targeted.

6 Archimonde, Hellfire Citadel 2.0

472 Attempts

• Expansion: Warlords of Draenor

Archimonde was the final and hardest boss of the Warlords of Draenor raid Hellfire Citadel, a callback to the dungeon of the same name from The Burning Crusade. Archimonde's fight required players to constantly be aware of each other and constantly communicate positioning, as well as random elements that turned the boss fight into a roll of the dice most of the time.

One such random element was the Doomfire spell, a spirit cast by Archimonde that dealt a massive amount of damage to a player for 10 seconds before switching to a new player. The spirit was tough to kill alongside Archimonde, and some raids turned all of their attention to the spirit once it spawned.

5 Yogg-Saron, Ulduar

More Than 500 Attempts

• Expansion: Wrath of the Lich King

Yogg-Saron is an Old God in World of Warcraft, a family of near-omnipotent ancient beings that envelop and consume worlds across the universe. While the version players fought in Ulduar in Wrath of the Lich King only used a fraction of its true power, it nonetheless proved tough, especially on its hardest difficulty.

The raid was designed so that Watchers and NPCs could be summoned and help the raid groups in defeating the Old God. For maximum difficulty, some guilds ignored these Keepers, choosing to take on Yogg-Saron without this help. The attempt cited here was accomplished without their aid. Yogg-Saron with no Keepers assisting was, at the time, considered to be one of the most difficult fights in the game. At the time, it was believed that Yogg-Saron was, according to the community, mathematically impossible. Ultimately, this was proven wrong by STARZ.

4 Ragnaros 2.0, The Firelands

More Than 500 Attempts

• Expansion: Cataclysm

Ragnaros was a boss in Vanilla World of Warcraft who received a revival in Cataclysm's Firelands raid. It was not a particularly tough fight for any unfair or broken mechanics (although it certainly wasn't a walk in the park). It was tough because it took most guilds more than 20 minutes to complete, though it wasn't one of the hardest raid bosses in WoW.

20 minutes is a long time for mistakes to happen, and even one or two party members' deaths could jeopardize the fight in the long run. Focusing for a third of an hour on pinpoint precision and timing is tiring. It's no surprise many guilds simply stopped keeping track of attempts out of tedium.

3 Garrosh, The Siege of Orgrimmar

638 Attempts

• Expansion: Mists of Pandaria

Garrosh holds a unique spot on this list as one of the few bosses who can claim a massive number of attempts in the 10-man raid category. In Mists of Pandaria 10-man raids and 25-man raids dropped the same loot, and while his fight was not particularly difficult due to one mechanic, like Ragnaros it just went on for absolute ages.

The fight takes place in various locations and has several phases. Players had to be on point and exactly correct with their timing if they wanted to down Garrosh, and that's quite hard to do over an average of 15 minutes.

2 Kil'Jaeden, The Tomb of Sargeras

654 Attempts

• Expansion: Legion

Kil'Jaeden was the final boss of Legion's Tomb of Sargeras, following the Fallen Avatar fight. Upon release, the Kil'Jaeden fight was bugged, so much so that some guilds stopped running the boss altogether until a fix came out. Kil'Jaeden's abilities also did far too much damage for healers to mitigate, almost as if the developers wanted to design a functionally impossible raid.

Eventually, Kil'Jaeden fell, and after a round of debuffs, more than a few guilds got in on the action. But at 654 attempts, Kil'Jaeden lived up to his title as the Supreme Commander of the Burning Legion and put up quite a fight to match, solidifying him as one of the most iconic WoW bosses.

1 Uu'nat, Crucible of Storms

731 Attempts

• Expansion: Battle for Azeroth

Uu'Nat in Battle for Azeroth's Crucible of Storms is the unquestioned hardest boss in WoW history as the most attempted raid boss in the game, and it's because of one troublesome mechanic. Unstable Resonance was an ability that affected more than half of the raid and forced players to avoid teammates who had a different resonance type from them. If players touched and had different debuffs, the ability would trigger and deal a lethal explosion within 10 yards of the players.

It was the hardest WoW boss at the time and one that required a lot of patience to overcome. Eventually, it was completed, but not without a complaint from the World of Warcraft community on the design of the Mythic difficulty mechanics.