Cthulhu, The Great Old One

Aura of Madness. Any creature that starts its turn within 60 feet of Cthulhu and can see or hear it must succeed on a DC 25 Wisdom saving throw or become frightened for 1 minute. A creature that fails this save by 5 or more is afflicted with short-term madness (as described in the Dungeon Master’s Guide). A creature can repeat the saving throw at the end of each of its turns, ending the frightened condition on itself on a success. If a creature’s saving throw is successful or the effect ends for it, the creature is immune to Cthulhu’s Aura of Madness for the next 24 hours.

Innate Spellcasting. Cthulhu’s spellcasting ability is Charisma (spell save DC 25, +17 to hit with spell attacks). Cthulhu can innately cast the following spells, requiring no material components:

• At will: detect thoughts, dissonant whispers (at 5th level), telekinesis

• 3/day each: dominate monster, feeblemind, power word kill

• 1/day: gate, time stop

Legendary Resistance (3/Day). If Cthulhu fails a saving throw, it can choose to succeed instead.

Reality Warp. Cthulhu’s presence distorts reality. At the start of each of Cthulhu’s turns, roll a d6 to determine an environmental effect within a 1-mile radius:

1. The ground trembles, forcing creatures to make a DC 20 Dexterity saving throw or fall prone.

2. A wave of psychic energy surges. Creatures within 120 feet must succeed on a DC 25 Intelligence saving throw or take 22 (4d10) psychic damage and be stunned until the start of their next turn.

3. Illusory tentacles appear, grappling creatures within 60 feet (DC 25 Strength saving throw to avoid).

4. The sky darkens, imposing disadvantage on Wisdom (Perception) checks relying on sight.

5. Gravity fluctuates, treating all creatures as if under the effects of a reverse gravity spell for 1 round (no save).

6. A rift to the Far Realm opens, summoning 1d4 star spawn (from Mordenkainen’s Tome of Foes) under Cthulhu’s control.

Regeneration. Cthulhu regains 30 hit points at the start of its turn if it has at least 1 hit point.

Multiattack. Cthulhu makes three attacks: two with its tentacles and one with its claw.

Tentacle. Melee Weapon Attack: +18 to hit, reach 20 ft., one target. Hit: 36 (4d12 + 10) bludgeoning damage, and the target must succeed on a DC 25 Strength saving throw or be grappled (escape DC 25). Until this grapple ends, the target is restrained, and Cthulhu can’t use this tentacle to attack another target.

Claw. Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 42 (5d12 + 10) slashing damage.

Eldritch Gaze (Recharge 5–6). Cthulhu fixes its gaze on a creature it can see within 120 feet. The target must succeed on a DC 25 Wisdom saving throw or take 55 (10d10) psychic damage and be afflicted with long-term madness (as described in the Dungeon Master’s Guide). On a successful save, the target takes half damage and is not afflicted with madness.

Dreams of R’lyeh (1/Day). Cthulhu projects a psychic vision of its sunken city, R’lyeh. Each creature within 120 feet of Cthulhu must make a DC 25 Intelligence saving throw. On a failed save, a creature takes 88 (16d10) psychic damage, is stunned for 1 minute, and gains a random form of indefinite madness (as described in the Dungeon Master’s Guide). On a successful save, the creature takes half damage and is not stunned or afflicted with madness.

Cthulhu 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. Cthulhu regains spent legendary actions at the start of its turn.

• Detect. Cthulhu makes a Wisdom (Perception) check.

• Tentacle Attack. Cthulhu makes one tentacle attack.

• Cast Spell (Costs 2 Actions). Cthulhu casts one of its at-will spells.

• Reality Shift (Costs 3 Actions). Cthulhu triggers its Reality Warp trait, rolling for an effect immediately.

If Cthulhu’s hit points are reduced to 0, it doesn’t die or fall unconscious. Instead, it enters a second phase, regaining 300 hit points and gaining the following mythic actions. Cthulhu can use these in place of its legendary actions during this phase.

• Awaken R’lyeh (Costs 3 Actions). Cthulhu summons a tidal wave of black water. Creatures within 120 feet must succeed on a DC 25 Strength saving throw or take 55 (10d10) bludgeoning damage and be knocked prone. On a successful save, a creature takes half damage and isn’t knocked prone.

• Eldritch Roar (Costs 2 Actions). Cthulhu emits a deafening psychic scream. Creatures within 60 feet must succeed on a DC 25 Constitution saving throw or take 33 (6d10) psychic damage and be deafened for 1 minute.