The Throne card in the Deck of Many Things (5e) says, "You gain proficiency in the Persuasion skill, and you double your proficiency bonus on checks made with that skill." If a 4th level Bard who chose Expertise in the Persuasion skill back at 3rd level draws this card, what happens to his proficiency bonus, which was already doubled because of the Expertise? Does it double again?
Also, if the events of that day's gaming session give him the XP for 5th level (at which base proficiency bonus goes up from 2 to 3), how will this affect the calculation moving forward?
Due to this Bard's extreme good fortune in card-drawing, he also drew a card that brought his already very high CHA score to 22, so we're pretty sure that no matter what happens, this is going to be one very persuasive bard, but we're not sure about stacking the doubling.
