The Auspicious and Useful God (Xiyong Shen) refers to the favorable Five Elements or Ten Gods in Bazi (Four Pillars of Destiny) analysis that benefit the命主 (Destiny Master). The Useful God is the most critical pivot in the chart, capable of balancing the entire configuration; the Auspicious God assists the Useful God. Determining the Auspicious and Useful God is the core step in Bazi analysis: when they are strong and unimpeded, destiny proceeds smoothly; when they are weakened or restrained, destiny encounters difficulties.
First assess the strength or weakness of the Day Master: if strong, favor elements that control, drain, or exhaust it (Direct/Seven Killings, Eating/Hurting Gods, Direct/Indirect Wealth); if weak, favor elements that generate or support it (Direct/Indirect Seals, Friend/Rob Wealth). The Useful God is the Five Element most urgently needed in the chart; the Auspicious God assists the Useful God. Specific identification requires comprehensive analysis of the relative strengths of the Five Elements within the chart.
For a Jia Wood Day Master with strong self-element, Geng Metal (Seven Killings) for control, Bing Fire (Eating God) for drainage, and Ji Earth (Direct Wealth) for exhaustion are auspicious and useful—thus Geng, Bing, and Ji constitute the Auspicious and Useful Gods.