What is the ruling on praying behind an Imam who consumes unlawful earnings, lies, swears falsely, violates people's honor, fabricates Hadith to deter people from legitimate acts of worship, and writes amulets?

The prayer behind a fasiq (transgressor) who lies, consumes unlawful things, and violates people's honor is valid, though disliked, if there is someone else from among the righteous. However, he should not be enabled to lead the prayer. As for one who writes shirk-laden amulets, prayer behind him is not permissible.