Devil's Sight. Magical darkness doesn't impede Abigor's darkvision.

Magic Resistance. Abigor has advantage on saving throws against spells and other magical effects.

Multiattack. Abigor makes four attacks using its Warhammer, Throwing Hammer, or a combination of the two.

Warhammer. Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit: 17 (2d8+8) bludgeoning damage plus 3 (1d6) thunder damage. 

Throwing Hammer. Ranged Weapon Attack: +15 to hit, range 30/60 ft., one target. Hit: 17 (2d8+8) bludgeoning damage plus 3 (1d6) thunder damage. Hammers thrown this way fall and stick into the ground after hitting their target and a new hammer appears in Abigor's hand.

Thunderous Slam (Recharge 5-6). Abigor causes all its hammers left on the battlefield to bristle with thunderous energy, exploding outwards with a roar. All creatures within a 10-foot-radius sphere centered on each hammer must make a DC 22 Constitution saving throw. Targets take 26 (4d12) thunder damage on a failed save, or half as much damage on a successful one. If a creature is within multiple spheres, it must make the save multiple times, taking damage from each source.

Abigor 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. Abigor regains spent legendary actions at the start of its turn.

Throw Hammer. Abigor makes a Throwing Hammer attack.

Call Thunder (Cost 2 Actions). Abigor targets a hammer that it can see within 60 feet to let out a thunderous roar. Creatures within a 10-foot-radius sphere centered on the hammer must make a DC 22 Constitution saving throw, taking 26 (4d12) thunder damage on a failed save, or half as much damage on a successful one.