Flame Resistant. 1/2 damage from fire damage.

Spellcasting Resistance. Has advantage on saving throws against spells 

Cobra Strike. Once per day can use its turn to go 120 feet and take a bite at an enemy.

Multiattack. Can attack 3 times on its turn.

Longsword. Melee Weapon Attack: +4 to hit, reach 5 ft., 1 target. Hit: 1 (1d8 + 4) [damage type] damage. 

Bite. Melee Weapon Attack: +6 to hit, range 10 ft., 1 target. Hit: 1 (1d6 + 2) [Piercing] damage. On hit Con save DC 15 or take 2D6 Poison Damage.

Stunning Strike. Once if a creature is in melee range the Yuan Ti Knight can use its shield to attempt to stun the opponent.  Con Save 12.