Skaab

Whenever the skaab starts its turn with 40 hit points or fewer, roll a d6. On a 6, the skaab goes berserk. On each of its turns while berserk, the skaab attacks the nearest creature it can see. If no creature is near enough to move to and attack, the skaab attacks an object, with preference for an object smaller than itself. Once the skaab goes berserk, it continues to do so until it is destroyed or regains all its hit points.
The skaab's creator, if within 60 feet of the berserk skaab, can try to calm it by speaking firmly and persuasively. The skaab 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 skaab ceases being berserk. If it takes damage while still at 40 hit points or fewer, the skaab might go berserk again.

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

The skaab is immune to any spell or effect that would alter its form.

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

The skaab has advantage on saving throws against spells and other magical effects.

The skaab's weapon attacks are magical.

The skaab makes two slam attacks.

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