Population Conversion
Conversion of a population to one religion or the other occurs passively, meaning that the presence of an agent in a province of the opposite religion is enough to slowly bring the population over to his point of view.
Character Conversion
A monk or missionary can convert an equivalent enemy agent, causing him to leave his position for a life of religious contemplation. In most case the agent will enter a monastery for a number of turns before returning to his clan capital; in extreme cases he will remain in the monastery indefinitely. Simply select your monk or missionary, right-click on your target agent and select character conversion from the options presented to you.
Incite Revolt (Shogun 2)
Monks and missionaries in Shogun 2 can incite a population to revolt through their powerful rhetoric. This is always extremely difficult to do in a province where a high percentage of the population follow the same religion as the agent. The subsequent insurrection will always be a peasant revolt, but if the monk incites the peasants they will be joined by Buddhist warrior monks. To incite, simply select your monk or missionary, right-click on your chosen target and select incite from the options presented to you. Remember, there is always a risk that trying to incite revolt will lead to the capture and execution of your agent.
Demoralisation
A monk or missionary can demoralise an enemy army, significantly lowering its morale and will to fight through his fiery rhetoric. Simply select your monk or missionary, right-click on your target army and select demoralisation from the options presented to you. The demoralisation effect will last from the successful completion of the action through to the beginning of the enemy's turn, allowing you a small window of time within which to attack their demoralised army.
Inspire Army
When inside an army belonging to their clan, a monk or missionary will inspire loyalty in them, reducing the chances that the garrison will be bribed. The inspiration effect will last as long as the agent is inside the army in question.
Indoctrination
In the Rise of the Samurai campaign a sou can indoctrinate a rival agent, but not a general , causing him to retire from his position for a life of religious contemplation. In most cases the agent will enter a monastery for a number of turns before returning to his lord's capital; in extreme cases he will remain in the monastery indefinitely. Simply select your sou, right-click on your target agent and select indoctrination from the options presented to you. However, bear in mind that there is a chance that your agent may be caught and executed should he fail.