Primal Grounds (始まりの地), also known as Singularity of the Origin in Falcom's romanisation, are subterranean chambers built to suppress the power of ancient artifacts and to keep their influence in check.
One Primal Ground is built beneath the Grancel Cathedral in the City of Grancel, Liberl. It was built in accordance with agreements between the Septian Church and the Royal Family. It holds the Recluse Cube. Another Primal Ground is built underneath the Aster House in mid-western Zemuria. There the artifact Loa's Spear was held when it caused the manifestation of Kevin Graham's stigma.
In front of the tree in the Hermit's Garden in Trails in the Sky the 3rd, Ries Argent reads an excerpt from the Book of Genesis, Verse 7, called 'Primal Ground': "That big tree has taken root on the banks of the seven-coloured spring, and brought about grace and delight".
According to Wazy Hemisphere, the Azure Tree is similar to the Primal Grounds in that it makes use of the septium veins to increase their reach and power. Since most, if not all buildings of the Septian Church are built on top of septium veins, it would make them a logical place to build the Primal Grounds.