You are the true God of Xanthuru because you created it, you control everything about it... and in short, you stand in the same relation to Xanthuru as the Triune God does to Earth. But that doesn't necessarily mean that the people of Xanthuru know anything about you (though the Seelvah at least have probably worked out that you exist.)
The two false religions are the worship of the Ley-heart and the Verdant, neither of which is accurate.