I'll have to read up on my lore.  The two characters I have are a young witcher who can find, follow around, and be a general nuisance to an older more experienced witcher if we have one, and a sorceress girl who befriended a fiend when she freed it from an abandoned trap and healed it.  
Maybe we could have a quest based plot like in the games?  Like have an overarching quest but have side quests along the way as our hero travel to different towns?