This is homebrew, submitted by a member of the community.
Rat King
Rat King
Medium monstrosity, chaotic evilMedium monstrosity, chaotic evil20 ft. Burrow30 ft.
20 ft. Burrow
SPECIAL TRAITS
Keen Smell. The rat king has advantage on Wisdom (Perception) checks that rely on smell.Plague of Ill Omen. The rat king radiates a magical aura of misfortune. A creature that starts its turn within 15 feet of the rat king must succeed on a DC 14 Charisma saving throw or have disadvantage on attack rolls and saving throws until the start of its next turn.
SPECIAL TRAITS
Keen Smell. The rat king has advantage on Wisdom (Perception) checks that rely on smell.
Plague of Ill Omen. The rat king radiates a magical aura of misfortune. A creature that starts its turn within 15 feet of the rat king must succeed on a DC 14 Charisma saving throw or have disadvantage on attack rolls and saving throws until the start of its next turn.
Actions
Multiattack. The rat king makes two Bite attacks.
Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 10 (2d6+3) piercing damage plus 7 (2d6) poison damage. If the target is a creature, it must succeed on a DC 14 Constitution saving throw or suffer one level of exhaustion and become infected with a disease. Until the disease is cured, at the end of each long rest, the creature must repeat the saving throw. On a failure, the creature suffers another level of exhaustion. The exhaustion lasts until the creature finishes a long rest after the disease is cured. A creature that succeeds on two saving throws recovers from the disease.
Call Rats (1/Day). The rat king magically calls 2d4 rats, 1d4 giant rats, or 1 swarm of rats. The rates arrive in 1d4 rounds, acting as allies of the rat king and obeying its spoken commands. The rats remain for 1 hour, until the rat king dies, or until the rat king dismisses them as a bonus action.
Multiattack. The rat king makes two Bite attacks.
Bite. Melee Weapon Attack: [+6] to hit, reach 5 ft., one target. Hit: 10 ([2d6+3]) piercing damage plus 7 ([2d6]) poison damage. If the target is a creature, it must succeed on a DC 14 Constitution saving throw or suffer one level of exhaustion and become infected with a disease. Until the disease is cured, at the end of each long rest, the creature must repeat the saving throw. On a failure, the creature suffers another level of exhaustion. The exhaustion lasts until the creature finishes a long rest after the disease is cured. A creature that succeeds on two saving throws recovers from the disease.
Call Rats (1/Day). The rat king magically calls [2d4] rats, [1d4] giant rats, or 1 swarm of rats. The rates arrive in [1d4] rounds, acting as allies of the rat king and obeying its spoken commands. The rats remain for 1 hour, until the rat king dies, or until the rat king dismisses them as a bonus action.
Legendary Actions
REACTIONS
Absorption. When a friendly rat, giant rat, or swarm of rats starts its turn within 5 feet of the rat king, the rat king can absorb it. If the rat king does so, the target dies, and the rat king gains temporary hp equal to the target’s remaining hp.
REACTIONSAbsorption. When a friendly rat, giant rat, or swarm of rats starts its turn within 5 feet of the rat king, the rat king can absorb it. If the rat king does so, the target dies, and the rat king gains temporary hp equal to the target’s remaining hp.
Details
A great knot of scabrous rats scrabbles together as a mass, with skulls, bones, and flesh entangled in the whole.
Teeth, eyes, and fur all flow as a single disturbing rat swarm walking on two legs.
Fused at the Tail. A rat king forms when dozens of rats twist their tails together in a thick knot of bone and lumpy cartilage—and offer praise to the rat demon Chittr’k’k. Its numbers and powers grow quickly.
Rule Sewers and Slums. The rat king is a cunning creature that stalks city sewers, boneyards, and slums. Some even command entire thieves’ guilds or hordes of beggars that give it obeisance. They grow larger and more powerful over time until discovered.
Plague and Dark Magic. The rat king is the result of plague infused with twisted magic, and a malignant ceremony that creates one is called “Enthroning the Rat King.” Rats afflicted with virulent leavings of dark magic rites or twisted experiments become bound to one another. As more rats add to the mass, the creature’s intelligence and force of will grow.
A great knot of scabrous rats scrabbles together as a mass, with skulls, bones, and flesh entangled in the whole.Teeth, eyes, and fur all flow as a single disturbing rat swarm walking on two legs.
Fused at the Tail. A rat king forms when dozens of rats twist their tails together in a thick knot of bone and lumpy cartilage—and offer praise to the rat demon Chittr’k’k. Its numbers and powers grow quickly.
Rule Sewers and Slums. The rat king is a cunning creature that stalks city sewers, boneyards, and slums. Some even command entire thieves’ guilds or hordes of beggars that give it obeisance. They grow larger and more powerful over time until discovered.
Plague and Dark Magic. The rat king is the result of plague infused with twisted magic, and a malignant ceremony that creates one is called “Enthroning the Rat King.” Rats afflicted with virulent leavings of dark magic rites or twisted experiments become bound to one another. As more rats add to the mass, the creature’s intelligence and force of will grow.
Shout outs: Stacey, Adam Fowler, Amanda Kettles, Angelo Anderson, Appreciate Witch of Life, AstroLass, bilbens baggo, Brian Nunziato, Bryan Sheairs, Brysen Packer, Bryson Waits, Burlyfighter, Caitlin W., Christopher Allbritton, CJMAXP, Connor, Dalton Elliott, Damon Carrington, Daniel Edwards, David Schraff, Dragons With Jetpacks, Elisa Martinez, eric sun, Ezzela1891, Federica Frezza, Gordon Alexander Fallon, Gundar Wez, Iofire, Irate The Pirate, Jade Arrowood, Jake Lane, Jeremiah Walker, Jess, Joe Dalby, John Nazario, JollyGamer, Jonathan Lekse, Jordan Brazeal, Joshua David Maddox, Justin Snyder, Kerry Melton, Kevin, KFB_Patreon, KingHavok1217, Kingyo Senpai, Kyle Clark, Lisa Tucker, Liz Fontain, Lizzie, Lou Bliss, Luke P, Mario Pizzamiglio, Mark L, Matt Yates, Max Hops, Maxwell Mayer, Michael Hamilton, Millergendraft, mtnman1979@aol.com, Mx Charlie, Mylon Schroder, Nahellion, Nathan, Nicholas Zamora, Nick Soucy, Phil Mehl, Phillip P Torchia, Pythor Sen, R., Rachel Anderson, Ray Bissonnette, Remora Jewel, Robert Rich, Robert Skadsem, Ryan Flagg, SallySparrow132, Sarah Holland, Serafina Moon, Shane Andrews, ShortyMcgibble, Sik Makoyi, Siren, Stefan Gottschalk's, Steve Rosenlund, Stuart, Syn21, That Video Editor Nic, thea musing, Trev909, Vedie V, Vincent Drone, Warren Clarida, Wesley Muncy, XMrMonkyx ., Zachary Burgess-Hicks, zachary gee, Zealot23, Zee Livezey
Their contribution stands as a beacon of hope for all adventurers!

