The Tesseract is an artifact discovered in the vaults of Flamerise by the Basilisk Knights. The artifact itself is a crystalline cube contained within a Mythril cubic armature. When activated, the image of one of the Progenitors appears and interacts with the individual that activated the artifact. The projected individuals, though condescending in their tone, are eventually helpful.
It was thru the use of the Tesseract that the Basilisk Knights were able to use the Progenitor artifacts and the mechanical remnants scattered throughout their protectorate.