Sail of the Black Opal
Wondrous Item,
Rare
(requires attunement; cost 2350 gp)
Crafting Components
Yard sail from a ship on its first voyage as a pirate or slaver ship, hair from a humanoid
Rumored to be crafted from the sailcloth of the notorious Black Opal, this heavy black canvas has been roughly sewn with human hair into a cloak.
As a bonus action you can expend one charge to call on the ship’s necromantic power and gain 1d4+4 temporary hit points. The sail has 3 charges and regains 1 charge for every hour spent submerged in seawater.
Additionally, if you are reduced to 0 hit points while attuned to this item, you immediately become stable as the hair burns to ash, blowing away at the faintest breeze and leaving behind a mundane piece of bone-dry sailcloth.
Source