whether through dark ritual or strength of will, youre body evolves to become closer to the serpentine perfection craved by the Yuan-ti people,

This Feat is repeatable up to 3 times. although each option can only be taken once

Serpentine head: 

your head transforms into a large snakes head

• Gain a natural weapon to use as an unarmed attack in the form of a bite attack for 1d4+your profiicency modifier piercing dmg and once per turn on a successful hit you can inject venom from your fangs,The creature must succeed on a Constitution saving throw or take an additional 3D6 poison damage.
• Gain the ability to cast Poison spray as a bonus action
• improve your perception score by +1

Serpentine Tail:

Your legs are transformed into a 15ft snakes tail 

• Constricting coils: you can grapple with your tail leaving your hands free for attacks and you count as one size larger for grapple checks and as a bonus action when grappling a foe you may constrict and attempt to crush the grappled target by beating 8+targets STR modifier and on a success the target takes 2D6 bludgeoning+STR modifier
• improve your strength score by +1

 Serpentine arms:

your arms transform into Snakes each ending in a Snake head the size of your hand previously

• Gain a natural weapon to use as an unarmed attack in the form of a bite attack with your arms for 1d4+your profiicency modifier piercing dmg and once(per arm) per turn on a successful hit you can inject venom from your fangs,The creature must succeed on a Constitution saving throw or take an additional 3D6 poison damage.
• gain the ability to see through eyes on your snake arms instead of your normal point of view at will
• improve your Dex score by +1
• gain +1 for grappling checks made using your arms 
• gain a disadvantage for skill checks using instruments and tools unlesss specifically modified for use