Prior to the orc races' corruption, Telkar Doomhammer lead the Blackrock clan. After Telkar died from old age, Blackhand took over to lead these orcs and soon fell under the manipulation of Gul'dan.
During the First War, the Blackrock orcs led the first charge. Near the end of the war, Blackhand was challenged and killed by his own lieutenant Orgrim Doomhammer. Doomhammer seized control of the clan and killed the members of the Shadow Council, the biggest threat to his throne.
Blackrock orcs also led the charge in the Second War. This time though, they one more battles, the betrayal of Gul'dan forced Orgrim to split up his people and force them to hunt down Gul'dan and his followers so they could slay him. The event weakened the Blackrock orcs, who were eventually defeated and nearly destroyed during the assault on Blackrock Spire, and Orgrim Doomhammer was 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 times, and soon enough their ranks began to swell again.
During the times between the Second and Third War, the Blackrock clan became a major problem for the Alliance. A faction in Lordaeron lead by a fel orc named Jubei'Thos re-embraced their demon worshiping, planned raids on various weak towns and when at the towns sacrificed villagers to the Burning Legion. They did this because the warlocks told them the demons would rain from the sky and that the world would burn. The Blackrock orcs also ignored Thrall's return to shamanism. During the Third War, most Blackrock orcs were slayed 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. 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 known simply as orcs of the Horde.
Aftermath of the Third WarEdit
Right now, the Blackrock clan currently resides in the Burning Steppes within their capital, Blackrock Spire. They were under the leadership of Rend Blackhand at that time. Soon after this, dark iron dwarves and Blackrock orcs began fighting each other. The Blackrock orcs have also still have holdings in the Burning Steppes and Redridge Mountains. Another rumor says that the Blackrock orcs have made an alliance with the black dragons of Nefarian. They are but one of the pawns Nefarian is using to undermine the human kingdom of Stormwind.
Since Deathwing's return, Blackrock orcs have become a major threat in Elwynn Forest and Redridge Mountains. In the Burning Steppes, they have been preparing for a huge assault on Redridge. Due to Nefarian and his father return they have allied themselves with Deathwing and they have become allies and members of the Twilight's Hammer.
A New BeginningEdit
After the Twilight's Hammer were defeated, Garrosh Hellscream, warchief of the Horde began recruiting many black orcs into his ranks. Garrosh's bodyguard by the name of Malkorok, who is of Blackrock clan descent. The Kor'Kron Guard also has a a number of black orcs that were recently recruited. The role of the recent Horde-aligned black orcs is somewhat like a secret force of police and want all people of the Horde to be loyal to the Warchief. The Horde-aligned black orcs want loyalty in the Horde so much that they will slay anybody who seems to cause problems or treason.