Part of Destiny: Nimble
Level 3
Stalker.
Advantage on Stealth checks when you are at full health. Weaken creatures have disadvantage on saves against you while Invisible or in stealth.
Vanishing.
If a creature dies from your Sneak Attacks, you can turn invisible until the start of your next turn or until you attack again. The next target you hit becomes Weakened.
Level 7
From the Shadows.
(2/encounter) When you land a Sneak Attack, you can force the target to make a STR save. On a fail your sneak attack dice deal maximum damage instead. Regain 1 use if they succeed.
Level 11
Voidform.
Gain a climbing speed and advantage on stealth checks regardless of health.
Level 15
Reap.
When you crit an enemy with fewer max HP than you, it dies.