Sharkrazor Mantle

Alter: While wearing this magic sharkskin cloak, you have a swim speed of 60 feet and can breathe underwater. When a creature successfully grapples or restrains you by touching you, that creature takes 1d6 piercing damage. A creature takes this damage again at the start of each of its turns while it maintains the grapple or restraint.

In addition, while wearing the cloak, you have advantage on Perception and Survival checks made to find or track a creature missing any of its hit points, and when you attack a creature you can't see thats below its hitpoint maximum, you make the attack as if you can see.

Attunement: Yes
Rarity: Rare
Type: Cloak
Cost: 630gp

Griffons Saddlebag, Vol 1