Based on this:
" You have reached the Efi Temple, a place of peace and serenity. Here be spoken the ways of Light, Love and Peace. We seek only to live in harmony with the nature sorrounding us, and aid the cosmos while becoming one with it."
There are three major concepts that can be extrapolated from that:
1) Peace and Serenity
2) Importance of Nature
3) Becoming one with the Cosmos
3) is the most rare so generally the easiest one to adress first. The only (well known) religions that stress this kind of cosmic monism which one has to be a part of would be Taoism and Hinduism. Mahayana Buddhism also has something like this although usage of a cosmic reality is not too common. All these religions will stress peace and serenity but I think the only one which makes a lot of it is Taoism. Taoism seems to be a lot like Efi actually.
Another interesting aspect is the darkness/light aspect which we used to bring up a lot. However we seem to agree that Light is nothing without darkness and darkness is nothing without light. If one lets go of comparisons they are essentially the same thing and meld in with each other. This captures the spirit of the Ying-Yang quite well too.
