Ok, first, read these two links:
viewtopic.php?f=10&t=620viewtopic.php?f=10&t=1253Summary: Östrons don't worship Creepers as some kind of god, but more like pay reverence to the Creeper spirits. Think of the Östron mythology as more of a nature spirit worship. There is no god, nor do Östrons necessarily exalt them as some all powerful entity. They do use it as a symbol to scare sometimes scare people, and of course small children as a kind of "boogeyman."
Fundamentalists take a different approach, but they wouldn't say there is just one god - just that only the creeper spirits are worth paying reverence to.
The Monastery in Arnum certainly could be a source for the fundamentalist element, however, that is less likely than some places in Östlaed. However, the Master of the Arnum monastery certainly would be one of these Fundamentalists.