The Ancient Reptile

Your patron is an ancient and immortal reptile from before the age of humanoid civilization. Your patron could be a Lizard, Snake, Turtle, Dinosaur or other reptile. It is unclear to you if this reptilian lord is a god, but you suspect it may predate the existence of the gods of humanoids. It tends to favor the wilds over civilization of humanoids and may even despise the very existence of organized civilization. The patron holds all reptilian species to be the highest form of beast, though respects other beasts for their usefulness and potential food. The motivations of the patron can vary depending on the type of reptile. A snake patron may want to infiltrate the government of a kingdom to assume control. A Turtle patron may seek peace, quiet and tranquility. A Dinosaur patron could want to see large reptiles retake the lands of civilized humanoids. A Lizard patron may just want to feast on insects, beasts, humanoids or any edible creatures. 

Your patron has great intelligence and it grants you spellcasting abilities by drawing from primal magics. You and your DM can decide if the patron speaks a language in order to communicate with you or if it simply communicates through ideas and emotions. 

Note/Reminder: Dragons and dragon-kin are not typically considered reptiles. Unless dragons in your homebrew world differ, dragons shouldn't be the patron for this subclass.

Expanded Spell List

The Ancient Reptile lets you choose from an expanded list of spells when you learn a warlock spell. The following spells are added to the warlock spell list for you.

Great Old One Expanded Spells

Spell Level	Spells
1st	Animal Friendship, Animal Messenger, Detect Poison and Disease, Purify Food and Drink, Speak with Animals
2nd	Alter Self, Darkvision, Enhance Ability, Locate Animals or Plants, Protection from Poison, See Invisibility
3rd	Conjure Animals, Water Breathing
4th	Compulsion, Greater Invisibility
5th	Cloudkill, Reincarnate

Reptilian Brain

You can telepathically speak to beast reptiles or humanoid reptiles (lizardfolk) within 30 feet.  

You also gain proficiency in nature, survival and animal handling.

Thermal Sight

You open your second set of eyelids to reveal your inner eye that can detect waves of light that are normally invisible to humanoids. Your eyes can now detect relative temperature up to 30 feet. You see cold creatures objects or environments as a shade of blue with the intensity of the cold increasing the brightness of the blue. You see hot objects, creatures, and environments as a shade of red, with the intensity of heat increasing the brightness of the red. Room temperature (70 degrees Fahrenheit) appears as black. This sight can penetrate non magical barriers that are 2 feet or smaller in thickness. This sight can penetrate non magical darkness only, unless you have darkvision that can penetrate magical darkness.

Cold-blooded creatures, creatures that don't have a internal heat source (like air elementals or undead) or objects that have the same temperature as their environment appear invisible when using this sight.

You can turn this sight off or on at will.

Potent Impotables

You become immune to the poisoned effect and poison damage.

In addition, 3 times per long rest you can add 2d10 poison damage to a weapon or spell attack on a single target. The target must make a constitution saving throw or become poisoned.

Regenerate

You gain advantage and can add your proficiency bonus to death saving throws.  You regain 1 missing hit point every 15 minutes when awake. You regain all missing hit points when taking a short or long rest. If you lose a limb, over the course of 10 days the limb will slowly grow back to it's full strength.