Inspiration. The Medusa starts each day with 3 inspiration points that she can use to reroll any attack, save or skill check or force an opponent to reroll one made against her.

Lightening Fast. The Yuan-ti Medusa is incredibly fast and hard to hit. She knows how to use her body to position herself without provoking attacks against her, often swinging her long snake body around and knocking enemies out of the way. The Yuan-ti Medusa never provokes attacks of opportunity, even from special class abilities and feats.

Innate Spellcasting. The yuan-ti’s innate spellcasting ability is Charisma (spell save DC 15). The yuan-ti can innately cast the following spells, requiring no material components:

At will: animal friendship (snakes only)

3/day: suggestion

1/day: fear

Legendary Resistance 3/day. If the Medusa would fail a saving throw she may succeed instead.

Petrifying Gaze. When a creature that can see the medusa's eyes starts its turn within 30 feet of the medusa, the medusa can force it to make a DC 16 Constitution saving throw if the medusa isn't incapacitated and can see the creature. If the saving throw fails by 5 or more, the creature is instantly petrified. Otherwise, a creature that fails the save begins to turn to porcelain 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 the medusa until the start of its next turn, when it can avert its eyes again. If the creature looks at the medusa in the meantime, it must immediately make the save.

If the medusa sees itself reflected on a polished surface within 30 feet of it and in an area of bright light, the medusa is, due to its curse, affected by its own gaze.

Multiattack  The yuan-ti Medusa makes three ranged attacks or three melee attacks, but can use its bite and constrict attacks only once each.

Slay the timid. The Medusa has advantage vs targets that avert their eyes from her.

Bite. Melee Weapon Attack: +11 to hit, reach 5 ft., one creature. Hit: 10 (1d10 + 5) piercing damage plus 17(5d6) poison damage.

Constrict. Melee Weapon Attack: +11to hit, reach 15ft., one target. Hit: 16(2d10 + 5) bludgeoning damage, and the target is grappled (escape DC 16). Until this grapple ends, the target is restrained, and the yuan-ti can’t constrict another target.

Scimitar. Melee Weapon Attack: +17 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) slashing damage.

Longbow. Ranged Weapon Attack: +17 to hit, range 200/600 ft., one target. Hit: 20 (2d8 + 10) piercing damage plus 10 (3d6) poison damage.

Point Blank Shot. When Medusa has her bow out and a creature enters within 10' of her she can make a point blank shot with advantage.

Medusa may make two legendary actions, choosing from any of the options below. Only one legendary action option can be used at a time, only once each round, and only at the end of another creature's turn. Medusa regains spent legendary actions at the start of her turn.

Snake Hair. After someone approaches Medusa she can have all of her snakes from her head attack an adjacent square. 2d8 snake heads automatically deal d6+1 piercing damage to one target. Each snake head also deals 1 poison damage.

Trip. Medusa uses her large snake body to slam it through opponents near her forcing them to dive for cover or be knocked prone. All creatures in a 15 cone must make a DC 16 dexterity saving throw or be knocked prone.