Spider Climb. The Underdark Horror can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Sunlight Sensitivity. While in sunlight, the Underdark Horror has disadvantage on attack rolls and on Wisdom (Perception) checks that rely on sight.

Thick Husk. The Underdark Horror has a minimum damage thresh hold of 10. If damage is sustained below this number the creature takes no damage.

Multiattack. The Underdark Horror can use its Maddening Presence and make 2 attacks: one with its bite and one with its claws.

Bite. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 14 (2d10 + 6) piercing damage a creature bitten must save on a DC 17 Con. Save or take 20 (4d10) poison damage and become poisoned for the next 24 hours taking 5 damage per hour poisoned.

Claws. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 24 (4d8 + 6) slashing damage.

Maddening Presence. The Underdark Horror targets one creature it can see within 30 feet of it. If the target can see or hear the Underdark Horror, the target must make a DC 17 Wisdom saving throw. On a failed saving throw, the target becomes paralyzed until the end of its next turn and adds one point of madness. If a creature’s saving throw is successful, the creature is immune to the Underdark Horror ’s Maddening Presence for the next 24 hours.