When an attacker that you can see hits you with an attack roll, you can take a Reaction to halve the attack's damage against you (round down).
When you deal Sneak Attack damage, you can add one of the following Cunning Strike effects. Each effect has a die cost, which is the number of Sneak Attack damage dice you must forgo to add the effect. The effect occurs immediately after the attack's damage is dealt.
If a Cunning Strike effect requires a saving throw, the DC equals 8 plus your Dexterity modifier and Proficiency Bonus.
Poison (Cost: 1d6): You add a toxin to your strike, forcing the target to make a Constitution saving throw. On a failed save, the target has the Poisoned condition for 1 minute. At the end of each of its turns, the Poisoned target repeats the save, ending the effect on itself on a success. To use this effect, you must have a Poisoner's Kit on your person.
Trip (Cost: 1d6): If the target is Large or smaller, it must succeed on a Dexterity saving throw or have the Prone condition.
Withdraw (Cost: 1d6): Immediately after the attack, you move up to half your Speed without provoking Opportunity Attacks.
As a Bonus Action, you give yourself Advantage on your next attack roll on the current turn. You can use this feature only if you haven't moved during this turn, and after you use it, your Speed is 0 until the end of the current turn.