Sources
CR
Type
Size
Alignment
Movement

Hythonia

Large Monstrosity, Lawful Evil

Armor Class 17 (natural armor)
Hit Points 199 (21d10 + 84)
Speed 40 ft., swim 40 ft., climb 40 ft.
STR
21
+5
DEX
17
+3
CON
19
+4
INT
14
+2
WIS
16
+3
CHA
18
+4
Saving Throws STR +11, CON +10, CHA +10
Skills Deception +10, Insight +9, Perception +9, Stealth +9
Damage Immunities poison
Condition Immunities Charmed, Frightened, Poisoned
Senses darkvision 120 ft., passive Perception 19
Languages Common
Challenge 17 (18,000 XP)

Traits

Legendary Resistance (3/Day). If Hythonia fails a saving throw, she can choose to succeed instead.

Petrifying Gaze. When a creature that can see Hythonia's eyes starts its turn within 30 feet of her, Hythonia can force it to make a DC 18 Constitution saving throw if she isn't incapacitated and can see the creature. If the saving throw fails by 5 or more, the creature is instantly petrified. Otherwise, on a failed save the creature begins to turn to stone and is restrained. The restrained creature must repeat the saving throw at the end of its next turn, becoming petrified on a failure or ending the effect on a success. The petrification lasts until the creature is freed by the greater restoration spell or other magic. Unless surprised, a creature can avert its eyes to avoid the saving throw at the start of its turn. If the creature does so, it can't see Hythonia until the start of its next turn, when it can avert its eyes again. If the creature looks at Hythonia in the meantime, it must immediately make the save. If Hythonia sees herself reflected on a polished surface within 30 feet of her and in an area of bright light, she is affected by her own gaze.

Shed Skin (Mythic Trait; Recharges after a Short or Long Rest). If Hythonia is reduced to 0 hit points, she doesn't die or fall unconscious. Instead, she sheds her skin, regains 199 hit points, and moves up to her speed without provoking opportunity attacks.

Spellcasting

Innate Spellcasting. Hythonia's spellcasting ability is Charisma (spell save DC 18). She can innately cast animate objects once per day requiring no material components.

1/day: animate objects

Actions

Multiattack. Hythonia makes three attacks: one with her claws, one to constrict, and one with her snaky hair.

Claws. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit:9 (1d8 + 5) slashing damage plus 4 (1d8) poison damage.

Constrict. Melee Weapon Attack: +11 to hit, reach 15 ft., one Large or smaller creature. Hit:16 (2d10 + 5) bludgeoning damage, and the target is grappled (escape DC 19). Until this grapple ends, the target is restrained and takes 15 (3d6 + 5) bludgeoning damage at the start of each of its turns, and Hythonia can't constrict another target.

Snaky Hair. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit:31 (4d12 + 5) bludgeoning damage, and Hythonia can pull the target up to 5 feet closer to her if it is a Large or smaller creature.

Legendary Actions

Move. Hythonia moves up to her speed without provoking opportunity attacks.

Snaky Hair. Hythonia makes one attack with her snaky hair.

Petrified Earth (Costs 2 Actions). Hythonia causes stone spikes to erupt from the ground in a 30-foot radius centered on her. The area becomes difficult terrain until the start of her next turn. Any creature, other than Hythonia, takes 9 (2d8) piercing damage for every 5 feet it moves on those spikes.

Mythic Actions

Numbing Claws. Hythonia makes two attacks with her claws. If both attacks hit the same creature, it takes an extra 7 (2d6) poison damage and must succeed on a DC 18 Constitution saving throw or become paralyzed until the start of her next turn.

Look at Me (Costs 3 Actions). Hythonia can force a sighted creature she has grappled to see her eyes and be affected by her gaze.

Lore

Theros's reclusive medusas often delight in collecting and expanding their galleries of petrified victims. Unlike other medusas, Hythonia isn't merely a collector; she's an artist.