Avenger

Construct.  Has no need to breath

Freedom of Movement. The Avenger ignores difficult terrain, and magical effects can't reduce its speed or cause it to be restrained. It can spend 5 feet of movement to escape from nonmagical restraints or being grappled.

Multiattack. The Avenger makes three attacks, Two with its bite and one with its ether Chain lightning or lightning bolt.

Bite. Melee Weapon Attack: +17 to hit, reach 5 ft., one target. Hit: 23 (3d8 + 10) piercing damage. ..

Chain Lightning . The Avenger magically creates a bolts of chain lightning from its mouth which can strike a target the avenger can see within 150 feet of it. Then three bolts leap to three other targets within 30 feet of the first target. A target must make a DC 23 Dexterity saving throw, taking 41 (10d8) lightning damage on a failed save, or half as much damage on a successful one.

Lightning Bolt. A stroke of lightning forming a line 100 feet long and 5 feet wide blasts out from its tail in a direction it chose's . Each creature in the line must make a Dexterity saving throw. A creature takes    50 (14d6) lightning damage on a failed save, or half as much damage on a successful one.

The Avenger  can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Avenger regains spent legendary actions at the start of its turn.

Create Mecha-Shark.  it constructs up to 2 Mecha-sharks that fight under its control.

Lightning Bolt. It can use its lightning bolt action.

Mecha-sharks use the same stat block as a giant shark but with the benefits of a construct.