The Waking Cathedral
Gargantuan undead, unaligned
Armor Class 19
Hit Points 468 (24d20 + 216)
Speed walk 20 ft.
Saving Throws STR +17, CON +16, WIS +11, CHA +12
Skills Athletics +17, History +9, Insight +11, Intimidation +12, Perception +11, Religion +9
Damage Resistances bludgeoning, piercing, and slashing from nonmagical attacks
Damage Immunities necrotic, poison
Condition Immunities exhaustion, frightened, paralyzed, poisoned, prone
Senses blindsight 120 ft., darkvision 240 ft., tremorsense 120 ft.
Languages Common, Giant, telepathy 120 ft.
Challenge 20 (25,000 XP)
Cathedral of the Colossus. The cathedral is part of a titan-sized body. It can move through spaces large enough for its Gargantuan form, and its movement shakes the ground. A creature that starts its turn within 30 feet of the cathedral must succeed on a DC 21 Strength saving throw or be knocked prone.
Siege Monster. The cathedral deals double damage to objects and structures.
Unquiet Nave. The cathedral cannot be surprised while it is conscious. It senses creatures touching or moving across its bones, stonework, or floors within 120 feet, even if they are hidden from its sight.
Magic Resistance. The cathedral has advantage on saving throws against spells and other magical effects.
Legendary Resistance (3/Day). If The Waking Cathedral fails a saving throw, it can choose to succeed instead.
Actions
Multiattack. The cathedral makes two Rib-Hammer attacks.
Rib-Hammer. Melee Weapon Attack: +17 to hit, reach 20 ft., one creature. Hit: 36 (4d12 + 10) bludgeoning damage. If the target is Huge or smaller, it must succeed on a DC 21 Strength saving throw or be pushed up to 20 feet and knocked prone.
The First Bell (Recharge 5–6). The cathedral tolls its heart-bell. Each creature of the cathedral’s choice within 120 feet that can hear it must make a DC 21 Constitution saving throw. On a failure, a creature takes 44 (8d10) thunder damage, is deafened until the end of its next turn, and is knocked prone. On a success, it takes half damage and suffers no other effect.
Rising Nave. The cathedral heaves upward as the titan beneath it begins to rise. Each creature on the ground within 60 feet must make a DC 21 Dexterity saving throw. On a failure, it takes 33 (6d10) bludgeoning damage and is knocked prone; on a success, it takes half damage and is not knocked prone. The area becomes difficult terrain until cleared.
Reactions
Stone Against Bone. When a creature the cathedral can sense deals damage to it while within 20 feet, the cathedral shifts a rib or buttress toward the attacker. The attacker must succeed on a DC 21 Dexterity saving throw or take 18 (4d8) bludgeoning damage.
Legendary Actions
The Waking Cathedral 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. The Waking Cathedral regains spent legendary actions at the start of its turn.
Grinding Step. The cathedral moves up to half its speed. Each creature within 10 feet of it when it moves must succeed on a DC 21 Dexterity saving throw or take 10 (3d6) bludgeoning damage.
Rib-Hammer. The cathedral makes one Rib-Hammer attack.
Echoing Toll (Costs 2 Actions). The cathedral releases a shuddering toll. One creature it can sense within 120 feet must succeed on a DC 21 Constitution saving throw or take 22 (4d10) thunder damage and be unable to take reactions until the end of its next turn.