Harpoon. Melee or Ranged Weapon Attack: +6 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 11 (2d6 + 4) piercing damage. If the target is a Medium or smaller creature, the merrow can pull it 10 feet closer.

Lightning Bolt (3rd-Level Spell; Requires a Spell Slot). The merrow unleashes a stroke of lightning in a line 100 feet long and 5 feet wide. Each creature in the line must make a DC 13 Dexterity saving throw, taking 28 (8d6) lightning damage on a failed save, or half as much damage on a successful one.