Dalatess Tidebringer

As part of a weapon attack, infuse your weapon with the might of the sea giantess. When you hit you deal 4d6 bludgeoning damage to your target, plus an additional 4d6 cold damage to your target and any creature behind it in a 15 ft. cone originating from the target.

At every level above 4th, the damage increases by 2d6 bludgeoning damage  2d6 cold damage.