Berserk. Whenever the lightning reaver starts its turn with 40 hit points or fewer, roll a d6. On a 6, the lightning reaver goes berserk. On each of its turns while berserk, the lightning reaver attacks the nearest creature it can see. If no creature is near enough to move to and attack, the lightning reaver attacks an object, with preference for an object smaller than itself. Once the lightning reaver goes berserk, it continues to do so until it is destroyed or regains all its hit points.

The lightning reaver's creator, if within 60 feet of the berserk lightning reaver, can try to calm it by speaking firmly and persuasively. The lightning reaver must be able to hear its creator, who must take an action to make a DC 15 Charisma (Persuasion) check. If the check succeeds, the lightning reaver ceases being berserk. If it takes damage while still at 40 hit points or fewer, the lightning reaver might go berserk again.

Aversion of Fire. If the golem takes fire damage, it has disadvantage on attack rolls and ability checks until the end of its next turn.

Immutable Form. The lightning reaver is immune to any spell or effect that would alter its form.

Lightning Absorption. Whenever the lightning reaver is subjected to lightning damage, it takes no damage and instead regains a number of hit points equal to the lightning damage dealt.

Magic Resistance. The lightning reaver has advantage on saving throws against spells and other magical effects.

Storm Coil. Whenever a creature ends its turn within 5 feet of the lightning reaver (including the lightning reaver itself), that creature must make a DC 15 Dexterity saving throw or take 5 (1d10) lightning damage. A creature has disadvantage on this saving throw if they are wearing metal armor or holding a metal object in one of their hands. The lightning reaver automatically fails this saving throw.

Magic Weapons. The lightning reaver's weapon attacks are magical.

Illumination. The lightning reaver sheds bright light in a 10-foot radius and dim light in an additional 10-foot radius.

Multiattack. The lightning reaver makes two slam attacks.

Slam. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) bludgeoning damage.

Fulmenic Discharge (Recharge 6). The lightning reaver releases electric bolts in three 30-foot lines originating from itself. Each creature in those lines (including the lightning reaver itself) makes a DC 15 Dexterity saving throw or takes 22 (4d10) lightning damage on a failed save, or half as much on a successful save. A creature only takes damage from this trait once, if at all. The lightning reaver automatically fails this saving throw.