Kraken Scale
Wondrous Item,
Uncommon
(cost 110 gp)
Crafting Components
The shed scale of a living kraken
This plump, palm-sized scale is pliant, and its mustard-green surface is tattooed with figures of sea monsters. It is also always slightly damp to the touch and gives off the faintest smell of brine.
When you are hit with an attack that would deal lightning damage, you can, as a reaction before damage is dealt, press the scale to give yourself Lightning resistance until the start of your next turn. Each time you do, roll 1d20 and subtract the amount of damage prevented. If the total is less than 1, the scale pops with a burst of seawater and a splash of seawater bursts from it as it loses its magical properties.
Source