Pre-requisites:

By performing rituals a Yuan-Ti Pureblood who has the Yuan-Ti Transformation (Stage Two) feat may further transform towards a more snakelike version of Yuan-Ti. In doing so the Yuan-Ti enhances its snakelike abilities. If the Yuan-Ti accentuates these features they are more acceptable to all Yuan-Ti communities.

Melee Bite Attack

To hit = Dex + Proficiency bonus

Reach = 10 ft.

Damage = 2d4 magical piercing damage + 1d10 poison damage.  

Maximum Frequency =Three times per round. As a bonus action a bite may be used in lieu of an off hand weapon to strike again as part of the same attack (in the same way that 2 weapon fighting allows a 2nd attack with an off hand). No free hand is needed in order to make a bite attack. 

Poison Spit Attack

To hit = Dex + proficiency bonus

Reach = 30 ft 

Damage: 3d6 poison damage. 

Notes:

Sneak attack damage, that would normally be able to be added to a melee or ranged attack, can be added on top of the Bite Attack or Poison Spit Attack.

Rituals have imbued the Yuan-Ti’s poison with supernatural power. Any creature poisoned by the Yuan-Ti must succeed on a constitution saving throw (save = 8 + con + proficiency bonus) or be unable to turn invisible for 1 minute.  

Wildshape

Twice per day, the yuan-ti can use its action to wildshape into a flying snake or a giant coral snake or back into its true form. Maximum duration in hours equals 1/4 of total character level.