Great Furnace contains canon BIONICLE info.
The Great Furnace was the largest furnace in Ta-Metru, and the hottest place there as well. Temperatures were so high that Matoran could not work inside for very long. It was here that flawed Protodermis creations are melted down for later recasting. The Morbuzakh thrived on heat, however, and therefore its King Root was located in the Great Furnace. The Toa Metru went inside to attempt to defeat it. It nearly destroyed them, but the power of the Great Disks created an energy sphere that imploded, destroying the root and ending the Morbuzakh's threat. The implosion reduced the Great Furnace to rubble. The Great Furnace was partially rebuilt by the Matoran after their return to Metru Nui. It was later restored by means of the Staff of Artakha.
Later, the Order of Mata Nui spread rumours through servants on Stelt that they had converted the Great Furnace into a Virus factory so that could recreate the protosteel-eating virus that killed Makuta Kojol, thus making Metru Nui a bigger target for Brotherhood of Makuta.
In the Reign of Fear alternate universe, the Great furnace was transformed into a prison. After they were captured by the Vahki in the archives, Antroz, Krahka, Keetongu and Savage were imprisioned here. However, they scaped, and the furnace was severally damaged when Savage went on a mad rampage. He fired a rocket at some Krahli, making the platform he and the Vahki were to fall to the lava. Savage was saved by Keetongu.