Clockwork Primordial

Clockwork Primordial. Any character fighting the clockwork Primordial can see that the complex arrangement of its workings gives it a unique vulnerability. Any character within 5 feet of the construct can use an action to attempt a DC 14 Dexterity check using jeweler’s tools or thieves’ tools. On a success, the behir takes 15 bludgeoning damage as it components start to grind, and it is no longer able to recharge its lightning breath nor use its wings for 3 turns.

Multiattack. The Primordial makes two attacks: one with its bite and one to constrict.

Bite. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 22 (3d10 + 6) piercing damage.

Constrict. Melee Weapon Attack: +10 to hit, reach 5 ft., one Large or smaller creature. Hit: 17 (2d10 + 6) bludgeoning damage plus 17 (2d10 + 6) slashing damage. The target is grappled (escape DC 16) if the behir isn't already constricting a creature, and the target is restrained until this grapple ends.

Lightning Breath (Recharge 5–6). The behir exhales a line of lightning that is 20 feet long and 5 feet wide. Each creature in that line must make a DC 16 Dexterity saving throw, taking 66 (12d10) lightning damage on a failed save, or half as much damage on a successful one.

Arc Lightning. Ranged Spell Attack: +7 to hit, range 30 ft., one target. Hit: 16 (3d10) lightning damage, and lightning jumps from the target to one creature of the Primordial's choice that it can see within 30 feet of the target. That second creature must succeed on a DC 15 Dexterity saving throw or take 13 (3d8) lightning damage.

Legendary Resistance (3/Day). If the Clockwork Primordial fails a saving throw, it can choose to succeed instead.

The Clockwork Primordial 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 tempest regains spent legendary actions at the start of its turn.

Move. Clockwork Primordial moves up to its speed.

Wing Attack (Costs 2 Actions). The Clockwork Primordial beats its wings. Each creature within 10 feet of the Clockwork Primordial must succeed on a DC 20 Dexterity saving throw or take 14 (2d6 + 7) bludgeoning damage and be knocked prone. The Clockwork Primordial can then fly up to half its flying speed.