This shard grants you a fraction of the power of a long dead sea serpent. You gain the following benefits:

Rime Breath. When you take the Attack action on your turn, you can replace one of your attacks with an exhalation of freezing cold waters in a 30-foot line that is 5 feet wide. Each creature in that area must make a Dexterity saving throw (DC = 8 + your Constitution modifier + your proficiency bonus). On a failed save, the creature takes 2d10 cold damage. On a successful save, it takes half as much damage. You can use this action a number of times equal to your proficiency bonus per long rest.

Deep Sea Resistance. You gain resistance to cold damage.

Notes: requires attunement