Multiattack

One Slam and two Claws or four Lightning Bolts.

Claw

Melee Weapon Attack: +13 to hit, 15 ft., one target, 26 (4d8+8) slashing damage. If target is Huge or smaller it is grappled (escape DC 19). Leviathan has two claws each of which can grapple only one target.

Slam

Melee Weapon Attack: +13 to hit, 5 ft., one target, 18 (4d4+8) bludgeoning damage and target: DC 19 Str save or be knocked prone.

Lightning Bolt

Ranged Spell Attack: +8 to hit 150/600' one target 17 (4d6+3) lightning.

Pylon Discharge (Recharge 5-6)

Discharges energy surge at a point it can see within 200' of it. Each creature within 30' of that point: 45 (10d8) lightning and is blinded until the end of its next turn (DC 19 Dex half damage not blinded).