The knowledge of rituals dedicated to channeling the powers of the chosen god for the benefit of the wider community. The skill of using and making holy items. Only very skilled priests can make holy items. The use or making of holy amulets, necklace or fetish-like objects. The use of powers and making of holy weapons.
Holy weapons are usually maces and staves.
The use and writing of scrolls, sheets of parchment that capture the power bestowed by one's god. The use and creation of all other holy items, like rings or sacred clothing. Only priests have need for faith, since it determines the amount of spell power their god grants them. Wisdom is the only important thing when it comes to faithfulness. The skills of persons with a sly criminal mind.