Blackrock clan

The Blackrock clan led the charge during the First War and Second War. During that time period, it was one of the largest and most feared of the orc clans. During the Third War a faction of the clan tried to summon demons, while another group is still fighting the Alliance and is known as the Dark Horde.

Pre Corruption
Blackhand was the Chieftain of the Blackrock Clan, but Gul'dan needed a puppet to control the Horde so Blackhand became a mere figurehead for the warlock.

First War
Near the end of the First War, Blackhand was challenged and killed by his lieutenant, Orgrim Doomhammer. Doomhammer seized control of the clan and slaughtered the members of the Shadow Council, the biggest threat to his throne.

Second War
The clan's forces achieved a number of victories during the Second War, though the betrayal of Gul'dan forced Doomhammer to divide his forces and send a part of the clan to hunt him down and slaughter his followers. The event weakened the Blackrocks, who were eventually defeated and nearly destroyed during the assault on Blackrock Spire, and Orgrim Doomhammer was himself captured and sent to Lordaeron in chains. The Blackrock clan did not disappear; though; the few remaining orcs who had not been captured or killed at the battle returned to Blackrock Spire and began to rebuild. Unlike the other orcs, they remained steadfast to the ideals of the old Horde, including demon worship and depraved blood lust. They became a beacon for orcs who longed for the old days, and soon enough their ranks began to swell again.

Third War
In the intervening years between the Second War and Third War, the Blackrock clan became a major problem for the Alliance. A faction in Lordaeron under the leadership of Jubei'thos re-embraced their demon-worshipping heritage, staged raids on a number of defenseless Alliance towns, and sacrificed their villagers to the Legion. They did this because their warlocks told them that demons would rain from the skies and the world would burn (referring to the coming of the Burning Legion in the following months). They also ignored Thrall's call to return to shamanism. During the Third War, most of the Blackrock forces in Lordaeron were killed by Arthas and Kel'Thuzad's Scourge. Jubei'thos and his lieutenants had in their possession a demon gate which Kel'Thuzad needed to communicate with Archimonde. The Blackrock orcs that Thrall didn't liberate from the humans' internment camps were likely killed by the Scourge.

However, other members joined the modern Horde under Thrall, like Eitrigg, and Varok Saurfang. Orgrim Doomhammer was a mentor to Thrall, and the orc capital of Orgrimmar was named after him. Regardless, the Blackrock orcs in the New Horde don't seem to have maintained a clan identity and are now simply Horde orcs.

Aftermath of the Third War
Currently, the Blackrock clan still mainly resides in and around Blackrock Spire under the leadership of Rend Blackhand, where they war with the Dark Iron dwarves for control of the area. Their holdings also include territory in the Burning Steppes and the Redridge Mountains. They have formed the Dark Horde and have become a dire threat to nearby towns like Lakeshire, whose defenses are severely strained against their raids. It has also been rumored that they have allied with a group of black dragons led by Nefarian, Deathwing's son. They are but one of the pawns Nefarian is using to undermine the human kingdom of Stormwind.

Cataclysm
During the Cataclysm, the Blackrock orcs have found a passage and invade Northshire Valley. It is revealed that the Blackrock clan have allied themselves with Deathwing and the Twilight's Hammer clan.

Mists of Pandaria
In the Mists of Pandaria, a large amount of Blackrock orcs have been granted to join the Horde at the request of Warchief Garrosh Hellscream. Led by Malkorok, hundreds of Blackrock orcs have been added into the elite Kor'kron while those have become citizens. Serving as a secret police force, they would punish those that who would dare stand against the Warchief. However, not all of the Blackrocks have been supportive to their warchief, finding him brutal and corrupt to all other Horde races. Most of them, along with the Dragonmaw, Orgrimmar Grunts, Durotar Orcs, and some of the Kor'kron have sided with Darkspear rebels when Thrall secretly entered Orgrimmar and rallied all the orcish citizens loyal to the Horde.

After the Siege of Orgrimmar?
During the Siege of Orgrimmar, their leader Malkorok was killed. It is unknown who will replace Malkorok as their chieftain, or if they ever will. It might be that Eitrigg, Varok Saurfang, or possibly Urukal would succeed Malkorok, as they are the only known living members having originated from that clan but are honorable enough to keep it under control. Either way, Thrall is believed to return as the racial leader of the orcs and Lord of the Clans, as he sought orcs in Orgrimmar who were against Garrosh's tyranny. No official Chieftain has been confirmed for the Blackrock Clan, post the Siege.

Warlords of Draenor
In the alternate timeline of Draenor, the Blackrock clan serves within the Iron Horde and is led by Blackhand himself.

Lordaeron divisions

 * Blackrock Raiders
 * Blackrock Scouts
 * Blackrock Slavers
 * Blackrock Warlocks
 * Blackrock Warriors

Azeroth divisions

 * Blackhand Legion
 * Bloodaxe Legion
 * Firebrand Legion
 * Scarshield Legion

Azeroth classes

 * Blackrock Ambusher
 * Blackrock Battlemaster
 * Blackrock Champion
 * Blackrock Gladiator
 * Blackrock Grunt
 * Blackrock Hunter
 * Blackrock Outrunner
 * Blackrock Raider
 * Blackrock Renegade
 * Blackrock Scout
 * Blackrock Sentry
 * Blackrock Shadowcaster
 * Blackrock Slayer
 * Blackrock Soldier
 * Blackrock Sorcerer
 * Blackrock Summoner
 * Blackrock Tracker
 * Blackrock Warlock
 * Blackrock Warrior