Mirrorworld Book 4: The Mad God of Mirrors - Mirrorworld, #4

Although he is now a god, Ric Storm tries to return to his old normal life. But he is consumed by strange desires he can no longer control and discovers he can make people do what he wants simply by commanding them. In his subconscious Stormwalker tells him that if he doesn't find some worshippers soon, sealing his position as a god, other deities will snuff him out of existence. Meanwhile, two old men from alternate Earths, a wizard and a priest, set out on separate journeys.
They are counterparts Klaus Streicher and Nick Stryker. Klaus, the wizard, journeys across the astral plane to the Science Earth, an aboriginal shaman named Wooreema as his guide, while the Nick, the priest, travels to Australia to start a new church called the Right Hand of God. Klaus and Nick are self-serving and hedonistic, but they end up on opposite sides in the battle to keep the New God from gaining followers.
Klaus and Wooreema team up with a homeless drunk named Tom who can see auras while Nick expands his church. Ric's wife Kerry joins the Right Hand of God and Nick welcomes her with open arms - literally. He becomes obsessed with her and arranges for his followers to abduct her. Ric never wanted to become a deity, but he realises he must use his new powers to rescue Kerry and fight the mages who are trying to bring about his destruction.
There is only one way Ric can succeed. He must call on the darkness within him, the darkness of Stormwalker.