A Rumor is a type of Mythos card. They will always have a blue background, and are significantly less common than either the green or yellow Mythos card. As with all Mythos cards, the number of Rumor cards, and the Phase in which they are placed, is determined by the Ancient One Sheet.
Once a rumor is put in play, the players usually must place a token on a space specified by the card, and then usually a number of Eldritch Tokens on the card, also specified on the card.
A Rumor is a long-lasting event that requires resources to complete, such as Clues. Usually, the player must complete one or more skill checks and spend clues in order to remove the rumor from play.
In general, an Eldritch Token is removed from the rumor in play when a Reckoning card triggers, and once there are none left, a powerful effect will harm the players. Some Rumors may even cause the players to lose the game.
If this powerful effect triggers and the game is not over, the Rumor is removed from play as it would be if the rumor was solved beforehand.