Multiattack

Three Claws attacks and one Tempest Trident attack or it makes three Lightning Ray attacks.

Claws

Melee Weapon Attack: +7 to hit, 5 ft., one target, 10 (2d6+3) slashing damage.

Tempest Trident

Melee Weapon Attack: +7 to hit, 5 ft., one target, 16 (2d12+3) piercing damage + 7 (2d6) cold. A creature hit by this: knocked prone (DC 16 Str negates) by a gust of wind channeled through the trident.

Lightning Ray

Ranged Spell Attack: +8 to hit, 150 ft., one target, 18 (4d8) lightning.

Crown of Water (1/Day)

The water on devil's head erupts in a geyser. Each creature within 10 ft. of devil: 35 (10d6) cold (DC 16 Con half). For 1 min when a creature enters a space within 10 ft. of the devil for 1st time on a turn or starts its turn there that creature: DC 16 Con save or take 10 (3d6) cold.