Snake-Eye Bones

Every trip to sea can become boring and one of the best ways to whittle away at the time—besides drinking rum—is to engage in a game of bones. Not every sailor on the high seas is honest and these dice were crafted with the devious amongst them in mind. Each four-sided die is made from bleached white whale bone and inlaid with jet-black markings. No matter how many times they are thrown or the number of ship hulls they strike, the dice never nick or scuff, and their markings do not fade. 

The dice have 2 charges and regain 1 charge each dawn. When you speak the command word as a bonus action as the dice are being rolled, their results come up as double ones (or snake-eyes). If you expend the last charge, roll a d20. On a result of 5 or less, the dice will roll up as double ones but both dice then crack in half rendering them useless.