80 Generic Regional Effects for Legendary Monsters
Header Image: Monster Manual (2008) by Wizards of the Coast / Michael Komarck
Legendary monsters are more than just a sack of hit points, killer breath, and a hunger for adventurers. They are more than just a single encounter, but rather a campaign arc. Their very presence seeps into the land, corrupting and changing it to fit a new habitat for them. When a legendary creature, like a dragon, makes its lair - the land changes to suit the legendary creature.
Below is a list of eighty generic Regional Effects that I use on my monsters to evoke their power and presence. Because they are generic, the monster name is simply ‘monster’. In addition, DCs formulas are provided, though the Ability modifiers are suggestions, not requirements.
Generic Regional Effects
Aberrant Master. All aberrations within 1 mile of the lair serve as the eyes and ears for the monster and can communicate telepathically with the monster.
Aberrant Worms. All beasts within (half Proficiency Bonus) miles are infested with worms, making them completely inedible. As they die, they rise as undead or aberrant creatures within 24 hours.
Acidic Water. Any sources of water within (half Proficiency Bonus) mile of the lair are transformed into acid after 1 hour of being exposed to the monster’s magic/presence.
Always Watched. Creatures within 1 mile of the monster's lair sometimes feel as if time has stopped or large portions of time have passed.
Aura of Apathy. Creatures within 1 mile of the monster’s lair experience a sensation of apathy and lack of will to go on. The sensation grows stronger the closer the creatures come to the monster’s lair and upon first seeing the monster, a creature must succeed on a DC (8 + Cha modifier + Proficiency Bonus) Wisdom saving throw or fall prone and become incapacitated when they first see the monster. This effect lasts until the end of their next turn as they are overcome with feelings of hopelessness.
Aura of Charm. Creatures have advantage on Charisma checks while in the lair.
Aura of Decay. All living creatures reduce their hit point maximum by 1d4 after every hour of being within (Proficiency Bonus) miles of the lair. This reduction lasts until the creature finishes a long rest outside the affected area.
Aura of Paranoia. Creatures within 1 mile of the monster’s lair sometimes feel as if their companions are lying to them and saying cruel insults just out of earshot.
Aura of Spirit. All living creatures regain an extra 1d4 hit points when they roll hit dice during a short rest while within (Proficiency Bonus) miles of the lair.
Burning Winds. Billowing hot wind rushes within (Proficiency Bonus) miles of the monster’s lair, sometimes forming superheated twisters that rip and tear through the area.
Burst of Color. Colors are extra bright and anything white, gray, or black is instead magically turned into a random color.
Carnage & Onslaught. The calm emotions spell, and similar magic, automatically fails if cast while in the lair.
Cavern Maze. Twisting tunnels underground form complicated mazes that can lead creatures astray. A false tunnel can appear and disappear as the monster wills it and can be discerned with a successful DC (8 + Wis modifier + Proficiency Bonus) Wisdom (Survival) check.
Celestial Respite. The land within (Proficiency Bonus) miles of the lair is under a constant hallow spell effect; celestials are allowed access and it has the Everlasting Rest effect.
Celestial Waters. The water sources within (Proficiency Bonus) miles of the lair are blessed and are treated as holy water. The water ceases being holy water after 24 hours of being away from the lair.
Charmed by Violence. Intelligent creatures within 1 mile of the monster’s lair are prone to complimenting the monster’s terror and heinous acts. A creature must make a DC (8 + Cha modifier + Proficiency Bonus) Charisma saving throw or become charmed by the monster and treat it as their friend when they first see it. This charmed effect breaks if they or their allies are attacked, otherwise, they will insist to everyone that they should get along and make a compromise to cause more havoc and commit heinous acts on the nearby villages.
Churning Current. The current is constantly changing within (Proficiency Bonus) miles of the monster’s lair, though it always seems to be trying to dash ships or creatures into sharp rocks or bunches of coral.
Constant Vigilance. Creatures within the lair always feel as if they’re being watched and listened to. The monster has hidden charms and other magic in the furniture of this lair that records spoken conversations and passes this information on to the monster.
Coral Reef. The waters within (Proficiency Bonus) miles of the lair are unnaturally warm, and coral grows in vibrant and vivid colors. The coral is unnaturally resilient and if a creature tries to swim it, they take 1d4 points of slashing damage per 5 feet moved through it. The coral is considered difficult terrain.
Damage: Number of d4s equal to half the creature’s Proficiency BonusCoral Reef Guards. Aquatic creatures such as fish, turtles and dolphins are fiercely protective of the reef and will try to attack intruders.
Coral Reef Toxins. If coral is broken, either on purpose or by accident, the coral releases dangerous toxins into the water, and any creatures within 10 feet of the broken coral must succeed on a DC (8 + Con modifier + Proficiency Bonus) Constitution saving throw or become paralyzed for an hour. They can repeat the saving throw after every 10 minutes.
Corn Maze. The crop rows within 1 mile of the lair twist and bend into a confusing maze with no end. These cornrows twist instantly, blocking creatures from escape. Moving 1 foot through the cornrows costs 3 feet of movement due to the thick rows and unnatural forces at work.
Dead Voices. Cold or hot wind blows through the land within (Proficiency Bonus) miles of the monster's lair with the voices of the dead whispering curses at those who couldn't save them.
Decaying Plants. Plants within (Proficiency Bonus) miles of the monster's lair grow, but are gray and devoid of any nutrition. No matter how many of them are eaten, they provide no sustenance and taste like ash and death.
Deep Pressure. The water pressure in a 1-mile radius of the lair is exceptionally powerful and every hour a creature spends in it must make a DC (8 + Con modifier + Proficiency Bonus) Constitution saving throw or suffer a level of exhaustion.
Desecrated. The area inside the monster’s lair is desecrated. If the land is purified, it becomes desecrated again in 1d4 hours. The smell of rotting flesh permeates the air.
Detect Presence. The monster is aware of other creatures within (half Proficiency Bonus) miles of its lair unless they are hidden by magic.
Difficult Currents. Currents are exceptionally treacherous within (Proficiency Bonus) miles of the lair. Any ability checks made to swim or safely navigate a vessel moving through these waters have disadvantage.
Difficult Terrain - Bog. The land within (Proficiency Bonus) miles of the lair takes twice as long as normal to traverse as it has turned into deep bogs.
Difficult Terrain - Detritus. Junk and clutter seem to collect in such thick piles that the ground within 1 mile of the monster’s lair is covered in litter and is treated as difficult terrain.
Difficult Terrain - Ice. The ground within (Proficiency Bonus) miles of the lair has been changed to ice and is considered difficult terrain.
Difficult Terrain - Trees. The land within (Proficiency Bonus) miles of the lair takes twice as long as normal to traverse as the trees themselves seem to move and landmarks are never consistent.
Disease Ridden. Diseases are widespread throughout the area within (Proficiency Bonus) miles of the lair. Any creature that spends an hour or more traveling in this area is targeted by a disease of the GM's choice.
Distracting Fragrance. Lightly fragrant air wafts through the structure, imposing disadvantage on any Wisdom (Perception) checks that rely on smell.
Divination Trap. Divination magic only works 10% of the time. When a creature attempts to cast a divination spell, the GM should roll a d100 secretly and, on a failure, the spell provides wrong information that will place a creature in great danger if they follow it.
Earthquake. Moderate earthquakes are common within (Proficiency Bonus) miles of the monster’s lair.
Eerie Songs. Creatures within 1 mile of the monster’s lair can hear eerie singing above the waters or through the water. Its song draws any creature further into the lair.
Extreme Temperature - Cold. The temperature of the area can plummet to extreme levels, causing tiny creatures to instantly freeze.
Extreme Temperatures - Heat. Intense heat burns the very air within (Proficiency Bonus) miles of the monster's lair. All creatures who spend at least an hour in the heat must make a DC 15 Constitution saving throw or suffer one level of exhaustion.
Far Realm Madness. When a creature hostile to the monster finishes a long rest within 1 mile of the monster's lair, roll a d20 for that creature. On a roll of 15 or lower, the creature's mind is warped by the Far Realm and they gain a long-term madness that lasts until they finish a long rest or a greater restoration spell or similar magic is cast. Roll on the long-term madness chart in the Dungeon Master's Guide on page 260.
Frightening Carnage. Carcasses of maimed and tortured beasts and humanoids hang from the trees with ill omens of death carved into them. Creatures must succeed on a DC (8 + Cha modifier + Proficiency Bonus) Wisdom saving throw or become frightened of the monster when they first see it. Once they encounter the monster, they can repeat the saving throw at the end of their turn, ending the effect on a success.
Glittering Lights. Small orbs of light that dance through the area are common within (Proficiency Bonus) miles of the monster’s lair.
Hive Mind. While a monster is within (Proficiency Bonus) miles of the lair, they can communicate with any other monster. The legendary monster can enter the senses of any monster that is part of the lair and see and hear through their senses. The legendary monster can also choose to talk through any monster in its lair.
Known Terrain. Difficult terrain is reduced in severity for the monster and its allies, decreasing the number of feet required to move 1 foot by 1. This means that most difficult terrain, which requires 2 feet of movement for 1 foot moved, is no longer difficult terrain.
Murderous Seaweed. Seaweed gathers in large clumps and any creature that moves within 20 feet of it must make a DC (8 + Wis modifier + Proficiency Bonus) Strength saving throw or be grappled. While grappled, the creature is restrained and the seaweed squeezes them tightly. At the start of a restrained creature's turn, they must make a Constitution saving throw or lose 1 minute of air as the seaweed squeezes their chest. It has AC 10 and (10 x half Proficiency Bonus) hit points, and it is vulnerable to slashing damage.
Music. Carnival music can be heard anywhere within the lair.
No Healing. Creatures attempting to cure a disease or heal hit points with magic must attempt a DC 10 ability check using their spellcasting ability. On a failed check, the spell or resources are wasted. If using a potion, hit dice, or other magic, the creature uses its Constitution modifier.
No Recovery. Living creatures are unable to expend Hit Dice to regain hit points while taking a short rest within the lair.
No Rest. If a creature is within 1 mile and attempts to use short-range teleportation magic, like misty step, dimension door or similar magic, there is a 5% chance that they will end up teleporting in a random direction.
Special: percent chance is equal to the monster’s Proficiency Bonus (for example, a +5 bonus would equate to 25%)No Secrets. Voices are twice as loud as normal and it is impossible to whisper while within the lair.
Obscured Insights. Enemies of the monster and its allies have disadvantage on all Wisdom checks when trying to gain information on them, like discerning tracks, counting the number of monsters, or assessing the skill of the monsters.
Obscured Terrain. Blowing dust and sand is constant within 1 mile of the lair, creating deep drifts and dunes. Survival checks made to track or find sustenance are made with disadvantage.
Obscuring Fog. Creeping fog within (Proficiency Bonus) mile of the lair lightly obscures the 20 feet in front of a creature and heavily obscures everything past that, making it impossible to see further.
Obscuring Freeze. Freezing fog heavily obscures the land within (Proficiency Bonus) miles of the monster’s lair.
Obscuring Gas. Sulphuric fog lightly obscures the land within (Proficiency Bonus) miles of the monster’s lair.
Obscuring Insects. Clouds of insects fill the lair, lightly obscuring anything that is 10 feet away or further. After 60 feet, the insects heavily obscure the area.
On Guard. The monster, and its allies, can not be surprised while in the lair. In addition, they have advantage on saving throws against being frightened or charmed.
Planar Portal - Air. Spinning vortexes within 1 mile of the monster's lair form portals to the Elemental Plane of Air, allowing creatures of elemental air into the world to dwell nearby.
Planar Portal - Ash. Obscuring smoke and ash form within 1 mile of the monster’s lair, creating portals to the Paraelemental Plane of Ash, allowing creatures of elemental air and fire into the world to dwell nearby.
Planar Portal - Earth. Rocky fissures within 1 mile of the monster's lair form portals to the Elemental Plane of Earth, allowing creatures of elemental earth into the world to dwell nearby.
Planar Portals - Fire. Burning wildfires within 1 mile of the monster’s lair form portals to the Elemental Plane of Fire, allowing creatures of elemental fire into the world to dwell nearby.
Planar Portal - Ice. Cracks through the snow and ice form within 1 mile of the monster’s lair, creating portals to the Paraelemental Plane of Ice, allowing creatures of elemental air and water into the world to dwell nearby.
Planar Portal - Magma. Fissures of magma within 1 mile of the monster’s lair form portals to the Paraelemental Plane of Magma, allowing creatures of elemental fire and earth into the world to dwell nearby.
Planar Portal - Metal. Strange portals within 1 mile of the monster's lair form links to the Elemental Plane of Earth, where elementals made of metal are sucked into this world, often to be fed upon by the monster. These portals are typically one-way portals, but a successful DC 15 Intelligence (Arcana) check can cause them to temporarily shift their direction.
Planar Portal - Necrotic. Rips in the Material Plane inside of the lair form portals to the Negative Energy Plane, allowing undead creatures to wander the lair.
Planar Portal - Radiant. Rips in the Material Plane inside of the lair form portals to the Positive Energy Plane, allowing celestial creatures to wander the lair.
Planar Portal - Ooze. Small pools of black grease within 1 mile of the monster’s lair form portals to the Paraelemental Plane of Ooze, allowing creatures of ooze, earth, and water into the world to dwell nearby.
Planar Portal - Water. Massive whirlpools spring up within 1 mile of the lair, forming portals to the Elemental Plane of Water, allowing creatures of elemental water into the world to dwell nearby.
Raging Emotions. Beasts, monstrosities, and similar creatures within (Proficiency Bonus) miles of the monster's lair become cruel and vicious, attacking others in a wild rage and with little thought. Even humanoids are short-tempered here and turn violent.
Repairing Structure. No dust settles in the monster’s lair and if an object or part of the structure is soiled, it is cleaned within 2d4 minutes. The lair is well maintained and anything that is part of the lair and breaks is immediately the target of a mending spell.
Roaming Rats. Oversized dire rats scurry through the fields within (Proficiency Bonus) miles of the lair, attacking any living creature they find.
School of Sharks. The area within 1 mile of the monster’s lair is infested with sharks.
Spider Presence. Spider webs within (Proficiency Bonus) miles of the monster's lair can take on dazzling colors or turn completely invisible.
Spider Spies. Small and tiny spiders within (Proficiency Bonus) miles of the monster are hostile to any creature that isn't a spider, biting and attacking any creature that attempts to rest near the lair. They also serve as eyes and ears of the monster.
Spider Storm. Strong winds will spontaneously form inside the caverns, bringing with them old webbing and baby spiders ballooning in the wind as it carries sweep them through the caves. Creatures caught in this wind stand a great risk of being caught up in a large web or being drowned in young, hungry spiders and any parent spiders watching over their young as they travel.
Spore Life. Organic matter begins to decay after 10 minutes within the lair, growing dangerous mold and fungi.
Teleportation Trap. The walls of the lair prevent creatures from teleporting in or out of the lair. Creatures are free to teleport once they enter the lair, so long as their destination remains on the inside of the lair. If a creature is inside the lair and attempts to teleport to the outside, they are instead brought before a place of the monster’s choosing. If a creature is outside the lair, and attempts to teleport inside, they are deposited just outside of the gates of the lair in front of the guards.
The Show Must Go On. All creatures become proficient with the Performance skill while they remain within the area of the lair.
Unending Thirst. Drinking sources within (Proficiency Bonus) miles of the lair are supernaturally fouled. Any outside creature that attempts to drink anything within this area immediately regurgitates it, including potions or elixirs.
Weather Control. Once per day, the monster can alter the weather in a (Proficiency Bonus)-mile radius centered on its lair. The monster doesn’t need to be outdoors; otherwise, the effect is identical to the control weather spell.
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