Serpent of the Dark

Preferable for non human, elf, dwarves characters or characters whose backstory is one of severe loss, classism, or brutality such as escaped slave.

Serpent Strike

When attacking from stealth (or are invisible) on an unaware, defenseless or engaged enemy you have advantage and +2 to attack rolls. On a successful sneak attack made in this way you release poison gas and inflict 15 poison damage in a 10 foot sphere on the target creature. This damage stacks with any other weapon or sneak attack damage.

Shed Skin

Successfully killing an enemy allows this character to cast invisibility on itself at no cost of action or bonus action. Invisibility is broken when this character attacks or a spell like dispel magic or another effect that disperses magic concealment effects this character.

Shadow Insight

Grants expertise to insight.

Shadows Embrace

Years of training have granted you the ability to sense movement from the ground, you gain tremor sense.  In addition you choose two ability scores and gain +1 to each.