Deadly Serpent

Very similar to assassins, Rogues of the Deadly Serpent specialize in taking out their targets quickly and effectively. However, the assassin's use of disguise and trickery proved ineffective for some, so the Rogues of the Deadly Serpent developed their own techniques based on hitting targets hard in the right spots.

Assassinate

Starting at 3rd level, you are at your deadliest when you get the drop on your enemies. You have advantage on attack rolls against any creature that hasn't taken a turn in the combat yet. In addition, any hit you score against a creature that is surprised is a critical hit.

Stun Lock

Starting at 3rd level, you can attempt to interrupt the nerves of your target by hitting them in just the right spot. When you make an attack that benefits from Sneak Attack, you can force the target to make a Constitution saving throw. The DC is equal to 8 + your prof. bonus + your DEX modifier. On a failed save, the target is stunned until the end of their next turn. Whether or not they fail the saving throw, you cannot use this against the same target until the next dawn.

Adrenaline Bloodlust

Starting at 9th level, you become more adept at getting yourself out of dangerous situations. At the start of your turn, if you are below 1/4 of your maximum hit points, you can use a bonus action to enter a state of adrenaline. While in this state, your movement speed increases by 10 feet and you gain a bonus to attack rolls made with melee weapons. The bonus equals half of your prof. bonus, rounded up. This state lasts for 1 minute, or until you end it as an action. When the state ends, you gain 1 point of exhaustion. When you use this, you cannot use it again until you complete a long rest.

Master Ambusher

Starting at 13th level  you gain advantage on initiative rolls, always being quick into the fight. Additionally, if you have the necessary materials, you can spend 10 minutes creating a trap. The trap is a 5 ft. cube and is very difficult to see. Creatures have a -5 to Wisdom(Perception) and Intelligence(Investigation) checks for the purpose of detecting the trap. When a creature enters the space of the trap, their speed becomes zero and they take 1d4 piercing damage. A creature can use their action to make a DC 15 Strength check to escape the trap. On a success, the trap is broken, and the creature regains their movement speed at the start of their next turn. On a failed save, their speed remains zero and they take an additional 1d4 piercing damage.

Serpent's Strike

Starting at 17th level, you become a master of instant death. When you attack and hit a creature that is surprised, it must make a Constitution saving throw (DC 8 + your Dexterity modifier + your proficiency bonus). On a failed save, double the damage of your attack against the creature.