The Piraka Stronghold is the heavily-armored fortress, which the Piraka, the rogue Skakdi and the former Dark Hunters, were resided in during their occupation in the island Voya Nui. It also appeared in the 2006 storyline in the BIONICLE series.
After their takeover on Voya Nui, the Piraka ordered the Matoran, who were corrupted by Makuta Teridax 's Antidermis to build the fortress near Mount Valmai, the volcano which located in the center of Voya Nui. After the completion however, the Matoran were forbidden to enter, with the exception of the prisoners. The stronghold also guarded by the numerous robotic machines called Nektann.
After being attacked by the Matoran Resistance, Avak retreated into the stronghold.