The Galtcreed Pact was one of the many failed attempts to govern Galt during its revolution. It is notable for disdaining the use of the notorious Final Blades to deal with political prisoners. Instead, a prison was built at a secret location in the Fog Peaks to house those the regime found to be inconvenient. It was known as Galtcreed, but came to be called the Dread Dungeons.
As with all such revolutionary governments, the Galtcreed Pact eventually fell, and its leaders were sent to the final blades. The location of the prison was never divulged to the new government.
A leading light of the Pact, Primarch Bremovir refused to give up the location even under torture—and a few weeks later it emerged that the "primarch" was actually an imposter. The real Bremovir fled in the night to the Dread Dungeons, and successive regimes have not been able to find him.