The majority of the carvings on the walls of the caverns under Fingol were etched using gryphon claws.
A truly grand entrance.
Fingol refers to the home of the Finn clan somewhere in Merseyside County. Underneath the house itself is the entrance to a systems of caves in which deceased members of the Finn clan have been buried since the 1400s. Despite the entrance to the cave being located in the basement of the Finn household, the actual caves are located somewhere within a rural area of the Merseyside County. Magic seems to have played a significant part in the formation of the caves, as besides the actual location being displaced far from the entrance, it is also mentioned in Page 1 of Illuminations that the entirety of the caves is contained in a space smaller than what it should require, hinting that the burial caves exist within a pocket dimension, temporal anomaly, or something of a similar effect.
The caves and their contents are tended to by the Finn Cave Guardian. This position is assigned to the first born of family within the Finn Clan who lives within close proximity to the Liverpool Avalon, and requires that they never travel abroad for the (currently unknown) duration of their duties. As of Illuminations, the next-in-line for the position of Cave Guardian is Paulbert James Finn, son of James Finn and resident of the Liverpool Avalon.