Kay

Kay is described by Will Hammond and the name is oft used as a blasphemy throughout Oakmont. Kay is the God of the organised religion in Oakmont, although it isn't explicitly stated there are crosses in their churches and a sculpture of the passion outside St. Michael's church in Advent.

Kay and the World
Kay doesn't seem to have much effect in the world unless he is merely a guise for Cthylla. Charles Reed however is discribed as 'Kay chosen' and the missing parts of the seal are known as Kay fingers. Whether or not this implys Kay chose Reed out of all the seeds to face Cthygonnaar or it is just a euphemism for Cthylla choosing him is uncertain.

Heresies and cults
There appears to be no sect or denomination within Oakmont which hasn't suffered some sort of perversion due to the presence of supernatural forces within the region. The remaining 'churches' are cults at best either serving a warped version of Kay or other forces. The two Charles Reed witnesses for himself are:

St. Michael's church of The burning Bush

Redemption Church

Kay and real world religion
It would seem that Kay is a euphemism for the Judaeo-Christian God. It is likely that this is due to the fact that the developers probably felt that forcing players to live in a world where this was overtly stated may have put players off.