The Mouse King

Large monstrosity, Lawful Evil

Armor Class 15 (natural armor)

Hit Points 210 (20d10 + 100)

Speed 40 ft., climb 30 ft.

STR 14 (+2) · DEX 18 (+4) · CON 20 (+5) · INT 16 (+3) · WIS 14 (+2) · CHA 16 (+3)

Saving Throws Dex +7, Con +8, Int +6, Wis +5

Skills Deception +6, Intimidation +6, Perception +8, Stealth +7

Gear 7 tiny golden crowns (worth 250 gp each), 1 Royal Rapier

Senses darkvision 120 ft., passive Perception 18

Languages Common, Undercommon, telepathy 60 ft. (with rodents only)

Challenge 7 (2,900 XP)

Traits

Seven Heads. The Mouse King has advantage on Wisdom (Perception) checks and on saving throws against being Blinded or Deafened. If the Mouse King takes bludgeoning damage, he becomes disoriented, losing these advantages and having his speed reduced by 10 feet until the end of his next turn.

Hive-Mind Master. As long as the Mouse King is not incapacitated, friendly rodents and rat swarms within 60 feet of him have advantage on their attack rolls.

Sunlight Sensitivity. While in sunlight or bright light, the Mouse King has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Actions

Multiattack. The Mouse King makes three attacks. He can replace one attack with his Spellcasting or his Squealing Terror (if available).

Royal Rapier. Melee Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) piercing damage plus 4 (1d8) poison damage. The target is automatically Poisoned until the end of its next turn.

Seven-Mouthed Bite. Melee Attack: +7 to hit, reach 5 ft., one target. Hit: 14 (3d6 + 4) piercing damage.

Squealing Terror (Recharge 5–6). The Mouse King’s seven heads unleash a deafening, discordant chorus of squeals. Each creature of the Mouse King's choice within 30 feet must make a DC 15 Constitution saving throw. On a failed save, a creature takes 21 (6d6) thunder damage and is Paralyzed until the end of its next turn. On a successful save, it takes half as much damage and is not Paralyzed.

Spellcasting. At Will: Animal Friendship (PHB, p. 239; rodents only), Command (PHB, p. 251; DC 14). 1/Day Each: Fear (PHB, p. 271; DC 14), Pass without Trace (PHB, p. 303)

Bonus Actions

Call the Horde. The Mouse King calls forth 1 Swarm of Rats in an unoccupied space within 30 feet of him. The swarm acts on the Mouse King's initiative, immediately after his turn. He can command a maximum of two swarms at a time through this ability.

Lore

A seven-headed monster embodying chaos and greed.

Who is the Mouse King?

In E. T. A. Hoffmann’s original tale, the Mouse King is a genuinely frightening, seven-headed monster—nothing like the garden-variety bad guys we usually meet. Every head wears a glittering gold crown, and all seven mouths squeak and hiss at once in a revolting chorus.

From Grimm Legends Bestiary 5E, p. 90 · Fern Flower Press