The Great Serpent

The Great Serpent is a powerful and enigmatic entity that resides in the depths of the cosmic realms, its essence intertwined with the primordial forces of chaos and mystery. A Warlock who pledges allegiance to the Great Serpent gains access to eldritch powers that are as elusive and unpredictable as the coils of the serpent itself. Some of these Patrons may be great serpent deities such a Sseth or Zehir, while others are eldritch beings with unknown origins. Many Yuan-Ti will seek out such a patron to become more snake-like, while others are drawn to seek out knowledge or simply for chaos and unpredictability of the Great Serpent. 

Patron Spells

At 1st level, your patron has taught you Detect Poison and Disease and Speak with Animals. These spells are considered Warlock spells for you and do not count against the number of spells known. Additionally you can cast Speak With Animals unlimited number of times, so long as it targets Snakes.

If you know the Eldritch Blast cantrip it can take the form of a needle laced with your patrons venom dealing poison damage instead of force. You must declare the type of damage dealt before each cast of the spell.

Semblance of the Serpent

At 1st level, your body begins to grow scales matching that of your Patron. These scales can be as sporadic or dense as you like. Additionally your patron empowers you with the agility and slipperiness of serpents. While not wearing armor your AC equals 13 + Dexterity modifier.

Venomer

At 6th level, your patron teaches you to use poisons of all sorts and allows you to tap into the potency of their own venom. You gain resistance to poison damage and advantage on saves against poisoned condition. You can use your Warlock DC instead of the base DC of poisons you craft or extract. Additionally poisons you craft or extract as well as poisons produced from your spells ignore resistance to poison damage.

Sense of the Serpent

At 10th level, your patron grants you the ability to perceive the world like snakes do granting you blindsight out to 10ft and advantage on perception checks that do not rely on sight.

Form of the Serpent

At 10th level, you patron has taught you how to morph into a great snake. Once per long rest, as a bonus action you can polymorpg yourself into a Giant Snake. You can maintain this form for 1 minute or until you drop to 0 hit points. Any excess damage carries over. The snake can look however you please, however it uses the Giant Constrictor Snake stat block with the following modifications.

• You retain your mental stats and your alignment
• Your to hit uses your melee spell attack modifier
• When transforming, you may forgo "Constrict" ability for Poisonous Fangs
  • Poisonous Fangs: Modifies the bite attack, on hit the target must make a constitution saving throw or take 3d8 poison damage or half as much damage on a successful one.

Venom Blood

At 14th level, your patrons mixes your blood with their venom which is an excruciatingly painful process but you come out of it with immunity to both poison damage and the poisoned condition. Furthermore, once per long rest, as a ritual, you can extract 2 doses of poison from your blood. When doing so you choose the type of poison: contact, ingested, inhaled, or injury. The target must make a constitution saving throw. On a fail the target takes 4d12 poison damage and is poisoned for 1 minute repeating the saving throw at the end of each of their turns. On a success they take half damage and is not poisoned.