Huge draconic monstrosity, herself

Armor Class: 20 (natural armor)

Hit Points: 310 23d12+161

Speed: 45 ft , fly: 75 ft , swim: 45 ft

STR

25 +7

DEX

13 +1

CON

25 +7

INT

13 +1

WIS

16 +3

CHA

19 +4

Saving Throws: Dex +9, Con +15, Wis +11, Cha +12

Skills: Arcana +9, Intimidation +12, Perception +19, Religion +9

Damage Immunities: acid, cold, fire, lightning, poison; bludgeoning, piercing, and slashing from nonmagical attacks

Condition Immunities: blinded, charmed, deafened, frightened, poisoned, stunned

Senses: darkvision 120 ft., truesight 60 ft.

Languages: Common, Draconic, Infernal, Undercommon, Underdraconic

Challenge Rating: 27 ( 105,000 XP)

Proficiency Bonus: +8

Actions

Multiattack. Karen makes three Bite attacks and one Tail attack.
Bite. Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 12 1d10+7 piercing damage plus 5 1d10 force damage.
Tail. Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 18 2d10+7 bludgeoning damage. If the target is a creature, it must succeed on a DC 22 Strength saving throw or be knocked prone.   Prismatic Breath (Recharge 4–6). Karen's heads exhale a single breath of multicolored energy in a 60-foot cone. Each creature in that area must make a DC 22 Dexterity saving throw. On a failed save, the creature takes 33 6d10 damage of a type chosen by Karen: acid, cold, fire, lightning, or poison. On a successful save, the creature takes half as much damage.

Legendary Actions

Legendary Actions. Karen can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. Karen regains spent legendary actions at the start of its turn.   Attack. The aspect makes one bite or tail attack.
Venomus Bite (Costs 2 Actions). The aspect makes one Bite attack. If the attack hits a creature, the target must succeed on a DC 27 Constitution saving throw or become paralyzed for 1 minute. The creature can repeat this saving throw as an action on its turn.