Spectral Grog



Spectral Grog is a drink that transforms you into a human pirate ghost for one hour.

Source
This item is occasionally dropped by the following:


 * Spectral Pirates and Rattling Mariners on the Timeless Isle
 * Salty Dregs, Brackish Cultivators, and Boneship Revelers at Isle of Shadows and nearby shore during Hallow's End

It can also be contained in Prince's Plunder chests at Oceanus Cove in Azsuna.