uh guys im too stupid to figure this riddle out but heres what I found:
Hermes is the messenger to Apollo and is related to Pandora box, as well as the "dozen" which I have found to been the gods of Olympus.(heremes is also an Olympian)
hepaestus is the god of volcanoes etc(or the craters)
and the three siblings he is talking about is the moirai
based on this I can conclude that it is hidden along the lines of greek mythology. and Moirai are also fate so maybe finding this shrine depends on fate?
also the moirai is found to be related to Apollo in the illiad by Homer.
also the kingdom of the moira is the kingdom of the limit and the end
from that I gather that it may be on an end portal or at the word border
and in the illiad appolo tries to stop patroculous in front of the walls of troy three times, and we commonly say "end dungeon" which is kind of a fortress.
anyways pls share the reward with me if I helped you out(im broke)
of course many of this may be off topic but that's what I found