Way of the Viper

You focused solely on the movements and abilities that a snake is capable of. As a result, your body became more nimble, and your unarmed strikes have adjusted to be piercing like a fang. You have also learned how to transmute your ki to be toxic like a vipers venom.

Creator Note: I would like some feedback on how to make this subclass better. I am aware that immunity and resistance to both the Poison damage and condition are very common, but I am lost at how to overcome this weakness.

Level 3: Viper's Strike

Starting at 3rd level when you select this subclass, your unarmed strikes embody the fangs of a viper. Once per turn. when you hit with an unarmed strike, you can deal Poison damage equal to your martial arts die + your Wisdom modifier. You can decide which unarmed strike to apply this bonus to after determining whether an attack hits or misses.

Level 3: Slithery Movement

Also at 3rd level, your nimble body allows you to move quickly and efficiently, even while you're surrounded. You can move through the space of another creature without the cost of extra movement. You cannot end your turn in the space of a creature the same size, one size larger, or one size smaller than you are.

Level 6: Hidden Viper

Beginning at 6th level, you have advantage on all Dexterity (Stealth) checks. In addition, you can also spend 1 Ki Point to take the Hide action as a bonus action.

Level 11: Venom Strike

At 11th level, you can use the Viper's Strike feature on every unarmed strike that hits. Additionally, you can apply the damage from the Viper's Strike feature on your monk weapons. You can also spend 1 Ki Point per hit with Viper's Strike to force a target to attempt a Constitution saving throw contested against your Ki save DC. On a fail, you inject venom from your weapon or unarmed strike, causing the affected target to take 1d6 Poison Damage at the start of its turn lasting 1 minute. The affected target can repeat the saving throw at the end of its turn to end the effect early.

Level 17: Medusa Form

Your adept abilities to be one with the snake have begun to affect your physical body. At 17th level, as an Action, you can spend 4 Ki Points to take on the form of a Medusa for 10 minutes, or you can end the transformation early on a Bonus Action. While in this form, you gain the following abilities:

- When a creature enters or starts its turn within 5ft of you, you can use your Reaction to make one attack with your snake hair, taking Piercing damage equal to your Martial Arts die + Wisdom modifier. This attack is considered magical for the purposes of overcoming resistance and immunity to non-magical attacks and damage. 

- You can use your Bonus Action to force one creature that you can see up to 15ft away from you to attempt a Constitution Saving throw contested against your Ki save DC. On a fail, the creature becomes frozen in place and is Petrified for 10 minutes. The Petrified creature can repeat the saving throw at the end of its turn to end the effect early. A creature who casts Greater Restoration or uses similar magic, can also end the effect early for the Petrified creature. This usage of the feature can be used a number of times equal to your Wisdom modifier.