I drew this color sketch in 2007 to cross section the swamp of Karda Nui.
The core of the Bionicle universe is inside this massive sphere of protodermis. When the heart is running this sphere is hanging in cero gravity in the centre of the heart firing ignition energy in all direction like a sparkplug in an engine. Now it is stuck in the swamp. But when ignited all matter around it in the heart will vaporise into pure energy. Matoro wearing the Ignika finally did the ultimate heroic deed and restarted the heart in 2008 sacrificing himself in the process.