This is my first time using charm monster as a DM or as a play. But what can i have them do to help the bbg in the party. They know this person is bad. so can i ask them to go down the tower and guard it fromintruders. Could i some how convince them that their is a family in more danger than what they are doing now. And how do i make it more affective against a paladin? Thanks for the help.
Charm spells are not mind control, so just keep in mind that they can't make a PC do anything they would not normally do. That said, use that limitation to be creative with how you apply the spell.