Kraken B{r}and

Alter: This metal sculpture of a tentacle coils around your arm as part of attuning to it. While you're attuned to the band, it can't be removed against your will, and you can magically transform the arm wearing it into a lashing tentacle as part of your attacks. When you take the Attack action, you can use your bonus action to make an unarmed strike using this tentacle, which has a range of 15 feet. On a hit the tentacle deals an extra 1d6 acid damage. When you attempt to grapple a creature, you can use the tentacle to target a creature within 15 feet of you that you can see, instead of within your normal reach. On a successful grapple, the creature is pulled up to 10 feet in a stright line toward you, and takes 1d6 acid damage a round while grappled in this way.

Attunement: Yes
Rarity: Very Rare
Type: Item
Cost: 31500gp

Griffons Saddlebag, Vol II

A group of pirates discovered that taking the band and heating it before someone attuned to it resulted in the band searing itself onto the attuner, all the way to the bone, permanently transfiguring the arm.