Trained Assassin

“Silent as shadows. Bold as night. Calm as wind. One shall die tonight.” 
― Ella Fleming-Christie, Crimson Exchange

You've had extensive training in the art of the silent kill, honing your skill with blade and shadow to uncanny levels. You are death personified. When wielding bladed weapons with the light property, you gain the Assassinate attack, as well as the following features:

• Exhaustive training in darkness has taught you how to become one with the shadows, and grants you a +2 bonus to stealth checks.
• Attacks made with light blades gain a +1 bonus to their critical range (you score a Critical Hit on a natural roll of 19 or 20).
• When wielding a light bladed weapon (dagger, handaxe, sickle, shortsword, scimitar), you gain access to the Assassinate attack.

Assassinate

• This attack can be used once per turn, as long as you have advantage on the attack roll.
• Assassinate adds  2d10 points of damage to a successful light bladed weapon strike.
• This damage increases to 3d10 at 5th level, 4d10 at 11th level and 5d10 at 17th level. 
• This additional damage does not stack with a rogue's sneak attack feature.