Curious about an error, just put together a bestiary and it had regional effects. The error is regionalEffectsFade: Field is missing. Pretty obvious, I just don't know where to add it. Below is an example monster: "name": "Ryu", "size": "gargantuan", "type": "dragon (kami)", "alignment": "chaotic good", "AC": "20 (natural armor)", "HP": "507 (26d20+234)", "speed": "40 ft., fly 120 ft., swim 120 ft.", "strength": 30, "dexterity": 10, "constitution": 28, "intelligence": 19, "wisdom": 22, "charisma": 30, "savingThrows": "Dex +9, Con +18, Wis +14, Cha +19", "skills": "History +17, Perception +15", "damageResistances": "bludgeoning, piercing, and slashing from nonmagical attacks", "damageImmunities": "cold, lightning, thunder", "conditionImmunities": "blinded, charmed, deafened, exhaustion, frightened, paralyzed, petrified, poisoned", "senses": "darkvision 240 ft., truesight 120 ft., passive Perception 25", "spells": "control weather, divine word, tsunami, whirlwind", "languages": "all, telepathy 120 ft", "challenge": "29", "traits": [{ "name": "Amphibious", "text": "Ryu can breathe air and water." }, { "name": "Aura of Vitality", "text": "Ryu and his allies within 30 feet of him regenerate 10 hit points at the start of each of Ryu’s turns." }, { "name": "Discorporation", "text": "When Ryu drops to 0 hit points or dies, his body is destroyed but his essence travels back to Tengoku, and he is unable to take physical form for a time." }, { "name": "Immutable Form", "text": "Ryu is immune to any spell or effect that would alter his form." }, { "name": "Innate Spellcasting", "recharge": "3/Day", "text": "Ryu can innately cast control weather, divine word, tsunami and whirlwind (spell save DC 27). his spellcasting ability is Charisma." }, { "name": "Legendary Resistance", "recharge": "3/Day", "text": "If Ryu fails a saving throw, he can choose to succeed instead." }, { "name": "Lightning Aura", "text": "At the start of each of Ryu’s turns, each creature of Ryu’s choosing within 10 feet of him takes 14 (4d6) lightning damage. A hostile creature that touches Ryu or hits him with a melee attack while within 10 feet of him takes 14 (4d6) lightning damage." }, { "name": "Limited Magic Immunity", "text": "Unless it wishes to be affected, Ryu is immune to spells of 5th level or lower. It has advantage against all other spells and magical effects." }, { "name": "Magic Weapons", "text": "Ryu’s weapon attacks are magical." }, { "name": "Atmospheric Hypoxia", "text": "Oxygen levels are lower within the Cleansing Cyclone, taxing most creatures that need to breathe. A creature must succeed a DC 10 Constitution saving throw at the start of each of its turns, or spend its action that turn gasping for air." }, { "name": "Heavy Precipitation", "text": "The heavy rains within the Cleansing Cyclone make the entire lair lightly obscured. Creatures within the area also have disadvantage on Wisdom (perception) checks that rely on hearing or sight, and open flames are extinguised." }, { "name": "Powerful Winds", "text": "A creature within the Cleansing Cyclone has disadvantage on ranged weapon attack rolls and Wisdom (perception) checks that rely on hearing. Any open flames are extinguished, fog is dispersed, and flying by nonmagical means is nearly impossible. A flying creature must succeed a DC 15 Strength saving throw at the end of its turn or fall." }], "actions": [{ "name": "Multiattack", "text": "Ryu casts a spell or controls a spell in a way that costs an action. He then makes three attacks: two with his claws and one with his tail." }, { "name": "Booming Tail", "text": "Melee Weapon Attack: +19 to hit, reach 25 ft., one target. Hit: 28 (4d8 + 10) bludgeoning damage plus 11 (2d10) thunder damage. If the target is a creature, it must succeed a DC 27 Strength saving throw or be pushed back 20 feet and knocked prone." }, { "name": "Tempestuous Claw", "text": "Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 24 (4d6 + 10) slashing damage plus 9 (2d8) lightning damage. If the target is a creature, it must succeed a DC 27 Constitution saving throw or become stunned until the end of its next turn." }, { "name": "Storm Breath", "recharge": "5-6", "text": "Ryu exhales lightning in a 10 feet wide, 120 feet long line. Each creature in that area must make a DC 27 Dexterity saving throw, taking 105 (30d6) lightning damage on a failed save, or half as much on a successful one." }], "legendaryPoints": 5, "legendaryActions": [{ "name": "Attack", "cost": 1, "text": "Ryu attacks with either his Booming Tail or his Tempestuous Claws." }, { "name": "Cast Spell", "cost": 2, "text": "Ryu casts a spell." }, { "name": "Deep Strike", "cost": 5, "text": "In a flash of lightning, Ryu disappears into the stormy skies above him. At the end of the next hostile creature’s turn, Ryu smashes into the ground with the force of a gigantic lightning strike. Each creature within 60 feet of the point of impact, must make a DC 26 Dexterity saving throw. A creature takes 70 (20d6) lightning damage on a failed save, or half as much on a successful one. The lightning ignites flammable objects in the area that aren’t being worn or carried." }, { "name": "Detect", "cost": 1, "text": "Ryu makes a Wisdom (perception) check." }, { "name": "Sonic Boom", "cost": 2, "text": "Ryu supercharges himself with lightning and instantly moves 60 feet in a direction of his choosing as he discharges the energy. Each creature Ryu passes through in that line takes 18 (4d8) thunder damage, and must succeed a DC 26 Strength saving throw or become knocked prone." }, { "name": "Wing Attack", "cost": 2, "text": "Ryu beats his wings. Each creature within 15 feet of Ryu must succeed a DC 27 Dexterity saving throw or take 24 (4d6 + 10) bludgeoning damage and be knocked prone. Ryu can then fly up to half his flying speed." }], "lairActions": ["**Lightning Strikes.** Ryu causes the Cleansing Cyclone to emit powerful lightning strikes. Until initiative count 20 on the next round, a creature is struck by lightning whenever it moves 10 feet unless it is submerged in water. Each lightning strike deals 7 (2d6) lightning damage. A creature hit by the lightning must succeed a DC 15 Constitution saving throw or be unable to take reactions until the start of its next turn.", "**Riptide.** Ryu causes powerful riptides in the water beneath the Cleansing Cyclone. Each creature in contact with the water except Ryu is moved 30 feet in a random direction. Roll a d8 to determine the direction for each affected creature.", "**Tempest.** Each creature not submerged in water other than Ryu is moved 30 feet in a random direction. Roll a d8 to determine the direction for all affected creatures.", "**Undertow.** Ryu targets a 20-foot radius area in the water that he can see. Until initiative count 20 on the next round, a creature that enters the area on its turn or starts its turn in that area must make a DC 27 Strength saving throw. On a failed save, a creature is moved 1d8 x 10 feet directly downwards. On a successful save, a creature is moved half that distance."], "regionalEffects": ["**Tengokuan Influence.** Living creatures in the area must roll on the table below at the end of every hour. Constructs, oni, oozes, and undead are unaffected. 1-4: Outgoing. The creature gains the following ideal: “I love being outside and dancing in the rain.” 5: Bane of Evil. The creature gains the following ideal: “I must eradicate evil wherever I find it.” 6: Fearlessness. The creature gains immunity to the frightened condition until the next time it finishes a short or long rest.", "**Extreme Cold.** The weather in the area is cold and damp. Each creature must succeed a DC 10 Constitution saving throw at the end of each hour or gain one level of exhaustion. Creatures with resistance or immunity to cold damage automatically succeed on the saving throw, as do creatures wearing cold weather gear (thick coats, gloves, and the like) and creatures naturally adapted to cold climates.", "**Frigid Water.** All water in the area becomes frigid. A creature can be immersed in frigid water for a number of minutes equal to its Constitution score before suffering any ill effects. Each additional minute spent in frigid water requires the creature to succeed on a DC 10 Constitution saving throw or gain one level of exhaustion. Creatures with resistance or immunity to cold damage automatically succeed on the saving throw, as do creatures that are naturally adapted to living in ice-cold water.", "**Strong Winds.** A creature within the area has disadvantage on ranged weapon attack rolls and Wisdom (perception) checks that rely on hearing. Any open flames are extinguished, fog is dispersed, and flying by nonmagical means is nearly impossible. A flying creature must succeed a DC 10 Strength saving throw at the end of its turn or fall.", "**Thunderstorms.** Thunderstorms. Thunderstorms rage within the area."]