https://orcpub2.com/pages/dnd/5e/mo.....s-of-mockfolk-
Name: Mockmaid/Mockmaidens (females of Mockfolk)
Option Source Name(e.g. Player's Manual, Hodor's Guide to Hodors): Natura Bestiam ex Gurgite membra

Challenge 15
Size Large
Type Monstrosity
Alignment Lawful Neutral
Armor Class 17
Speed: 30 ft., fly 40 ft., swim 50 ft., climb 10 ft.

Hit Points:
Die Count 16
Die 10
Modifier 73

Abilities:
Strength 18
Constitution 19
Dexterity 13
Intelligence 10
Wisdom 13
Charisma 18

Saving Throws:
Strength 6
Constitution 4
Dexterity 0
Intelligence 0
Wisdom 2
Charisma 1

Skills:
Acrobatics 1
Animal Handling 2
Arcana -
Athletics 6
Deception 8
History -
Insight -
Intimidation 10
Investigation 2
Medicine -
Nature 1
Perception 5
Performance 13
Persuasion 11
Religion -
Sleight of Hand -
Stealth 10
Survival 5

Languages: Abyssal, Common, Deep Speech, Dwarvish, Elvish, Giant, Gnomish, Goblin, Halfling, Orc, Primordial, Sylvan, and Undercommon.

Mockmaid/Mockmaidens (females of Mockfolk)
Large monstrosity, lawful neutral
Armor Class:17
Hit Points:16d10 + 73 (158)
Speed:30 ft., fly 40 ft., swim 50 ft., climb 10 ft.
STR
18 (+4)
DEX
13 (+1)
CON
19 (+4)
INT
10 (0)
WIS
13 (+1)
CHA
18 (+4)
Saving Throws:Str +6, Con +4, Dex 0, Int 0, Wis +2, Cha +1
Skills:Persuasion +11, Investigation +2, Acrobatics +1, Performance +13, Perception +5, Survival +5, Animal-handling +2, Nature +1, Deception +8, Intimidation +10, Athletics +6, Insight NaN, Stealth +10
Damage Vulnerabilities:acid, cold, fire, lightning, necrotic, radiant
Damage Resistances:acid, cold, fire, lightning, necrotic, radiant
Damage Immunities:slashing, poison, piercing, bludgeoning
Condition Immunities:blinded, deafened, stunned, unconscious, invisible
Languages:deep speech, orc, dwarvish, gnomish, sylvan, elvish, abyssal, common, undercommon, primordial, giant, halfling, goblin
Challenge:15 (13000 XP)
False Appearance.:While the Mockmaid remains submerged in water or mud/sand, it is indistinguishable from a normal humanoid, such as a member of the merfolk, sirens, skum, aquatic/sea elf, ect.
Amphibious.:The monster can breathe air and water.
Keen Hearing. :The creature has advantage on Wisdom (Perception) checks that rely on hearing.
Blood Frenzy. :The creature has advantage on melee attack rolls against any creature that doesn't have all its hit points but only underwater.
Actions
Bite. :Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 21 (5d6 + 4) piercing damage.
Tail Swipe/Sting.:The Mockmaid makes one tail attack. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 18 (4d6 + 4) bludgeoning damage. If the target is a creature, it must succeed on a DC 14 Strength saving throw or be knocked prone. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 13 (2d8 + 4) piercing damage plus 17 (5d6) poison damage, and the target must succeed on a DC 14 Constitution saving throw or become poisoned for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
Slam. :Melee Weapon Attack: +6 to hit, reach 10 ft., one target. Hit: 14 (3d6 + 4) bludgeoning damage.
Multiattack/Fist.:The mockmaiden makes 2-4 attacks: one each with its four arms and/or two with a 2 two-handed weapons. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 22 (3d10 + 6) bludgeoning damage.
Constrict. :Melee Weapon Attack: +10 to hit, reach 5 ft., one Large or smaller creature. Hit: 17 (2d10 + 6) bludgeoning damage plus 17 (2d10 + 6) slashing damage. The target is grappled (escape DC 16) if the mockmaid isn't already constricting a creature, and the target is restrained until this grapple ends.
Tentacles/slam.:One creature grappled by the Mockmaiden must succeed on a DC 13 Constitution saving throw or be poisoned for 1 minute. Until this poison ends, the target is paralyzed. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. The Mockmaid slams creatures grappled by it into each other or a solid surface. Each creature must succeed on a DC 14 Constitution saving throw or take 10 (2d6 + 3) bludgeoning damage and be stunned until the end of the mockmaid's next turn. On a successful save, the target takes half the bludgeoning damage and isn't stunned.
Tendril/Whiskers. :Melee Weapon Attack: +7 to hit, reach 50 ft., one creature. Hit: The target is grappled (escape DC 15). Until the grapple ends, the target is restrained and has disadvantage on Strength checks and Strength saving throws, and the Mockmaid can't use the same tendril on another target.
Ink Cloud:(Recharges after a Short or Long Rest). A 20- foot-radius cloud of ink extends all around the octopus(on the back of the Mockmaiden's lure head) if it is underwater. The area is heavily obscured for 1 minute, although a significant current can disperse the ink. After releasing the ink, the creature can use the Dash action as a bonus action.
Legendary Actions
Saw Tusk Attack/Gore.:Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) slashing damage. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 19 (3d8 + 6) piercing damage.
Swallow. :The mockmaid makes one bite attack against a Medium or smaller target it is grappling. If the attack hits, the target is also swallowed, and the grapple ends. While swallowed, the target is blinded and restrained, it has total cover against attacks and other effects outside the mockmaiden, and it takes 21 (6d6) acid damage at the start of each of the mockmaid's turns. A mockman can have only one creature swallowed at a time.
Amphibian Climb. :The Mockmaid can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check. Creature must keep at least 3 point of contact with a surface to maintain the climb.
Limited Telepathy. :The Mockmaid can magically transmit messages and images to any member of their own species as long as they are related and within 250 feet of it. This form of telepathy doesn't allow the creature to telepathically communicate to other races/species.
Regeneration. :The creature regains 10(-1 DEX each subsequent turn) hit points at the start of its turn. If the creature takes acid, fire, cold, or lightening damage, this trait doesn't function at the start of the Mockmaiden's next turn. The monster dies only if it starts its turn with 0 hit points and doesn't regenerate.