Armor Class 17 (natural armor)
Hit Points 228 (24d12 + 72)
Speed 40 ft., climb 40 ft.
Skills Perception +7, Stealth +8
Condition Immunities frightened
Senses darkvision 120 ft., passive Perception 17
Languages —
Challenge 15
Spider Climb. The horror can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.
Sunlight Sensitivity. While in sunlight, the horror has disadvantage on attack rolls and on Wisdom (Perception) checks that rely on sight.
Multiattack. The horror can use its Maddening Presence and make three attacks: one with its bite and two with its claws.
Bite. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 28 (4d10 + 6) piercing damage.
Claws. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 24 (4d8 + 6) slashing damage.
Maddening Presence. The horror targets one creature it can see within 30 feet of it. If the target can see or hear the 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. If a creature's saving throw is successful, the creature is immune to the horror's Maddening Presence for the next 24 hours.
Guildmaster's Guide to Ravnica, p. 205