Interlude 18: The Jonah
It's no secret that sailors are a superstitious lot, believing in all kinds of signs, practices, omens and other such things. Usually this just makes them more colorful characters, habits and tendencies that are entertaining but have little real effect on the world. Occasionally, however, these beliefs manifest in a way that is downright dangerous for the people involved.
The notion of a Jonah is an example of how superstition can turn nasty. Based on the story from the Bible, about a man who brings misfortune upon his ship because of his religious faith, a Jonah is a person who is believed to be bad luck, pure and simple. This association goes beyond avoidance or special treatment, though; other crew members begin wanting to eliminate the unlucky character so as to prevent call kinds of imagined calamities.
Note: This interlude is inspired by the movie Master and Commander: The Far Side of the World, a movie that provides an excellent depiction of life aboard a ship at sea.
The Rumor Begins
The belief that one of the characters aboard the ship is a Jonah can arise in a number of different ways. One possibility is that it is first mentioned in response to a disaster of one kind or another. For example, if a sailor was climbing the ropes but then took a nasty fall, or if there was a bad spell of weather for an extended period, that might be enough to provoke an accusation. In such a case, the GM could choose the victim of the claim based upon circumstance.
On the other hand, the idea that a member of the crew is a Jonah could also be raised by one character specifically as an attack against another. In this case, the idea spreads because one or more characters are telling it to others. This possibility could require some additional adjudication on the part of the GM, but could also make for a more intriguing series of events.
Dealing with the Problem
Once the rumor has started, it becomes very important for the PC's to deal with it. This is because other sailors begin plotting to take action against the accused, and because the Jonah in question begins to wonder if he/she is indeed a danger to the ship and crew. The GM could let the PC's discover the source of the rumor via a DC 20 Gather Information check; alternately, the situation could provide for extensive roleplaying. (As combination of the two elements is always an option, of course.) If the belief has arisen because of unfortunate events, the PC's might be able to quash it by demonstrating why those occurrences happened. In such an instance, they could make a DC 20 Diplomacy or Sway check to convince the superstitious crew members, with bonuses or penalties assigned for a particularly good speech or for providing convincing evidence.
On the other hand, if there is a specific culprit behind the rumors, exposing him/her could require a DC 20 Gather Information, along with more concerted action on the part of the PC's. This might entail spying on said character to overhear proof of the lie, or perhaps even a duel ashore in the tradition of pirate crews.
In either case, if the PC's fail to take the appropriate actions, the rumor of a Jonah aboard a ship could result in the maligned character trying to leave, or in the crew rising against him/her.
New General Fortune: Jonah
Your luck tends to be very strong--for good or for ill.
Drawback: For you the rules of one and twenty apply to all d20-based checks, not just to attack rolls and saving throws. Moreover, failure usually provides some kind of negative consequence, at the GM's discretion. This might include a failed Climb check causing a fall, a botched Concentration check resulting in a spell accidentally targeting an ally, or the like.