Veilblade

Veilblades are shinobi, assassins, and spies who specialize in a terrifyingly efficient form of combat known as the Art of the Spider Lily. Heeding the omen of the red blossom that blooms on the edge of the afterlife, they move like ghosts through the battlefield, their actions a beautiful and deadly farewell. Their techniques are not designed for prolonged duels, but for swift, final strikes that end confrontations in a heartbeat. They are masters of that single, perfect moment between a foe's stumble and their final fall—the moment of parting.

Fallen Petal

3rd-level Veilblade feature

You learn an esoteric breathing and movement technique that allows you to flow through combat like a specter. You gain proficiency in Survival skill if you don't already have it.
Additionally, Once on each of your turns when you make a melee attack that qualifies for your Sneak Attack, you can use your reaction to move up to 10 feet without provoking opportunity attacks from the target of that attack. This movement does not expend your movement speed. You still provoke opportunity attacks from other creatures as normal.

Silent Petal

3rd-level Veilblade feature

Your training attunes you to the veil between light and darkness. You gain 10 feet of darkvision (or increase your darkvision by 10 feet). Additionally, you have advantage on Dexterity (Stealth) checks to hide or to move silently while in an area of dim light or darkness.

Essence of the Final Bloom

9th-level Veilblade feature

Your art teaches you to harness the latent energy released at the moment of death. Immediately after you reduce a creature to 0 hit points with an attack on your turn, you gain temporary hit points equal to your rogue level.

Veil of the Blooming Petal

13th-level Veilblade feature

Your mastery of movement is now absolute. Your movement leaves no physical trace. You cannot be tracked by non-magical means.
Additionally, you can make a Dexterity (Stealth) check to hide even when you are only lightly obscured from a creature. When you successfully hide in this way, your presence is briefly marked by a faint, supernatural scent of spider lilies. This fragrance has no mechanical effect by itself but can be detected by other creatures and may hint at your passage. You can use this benefit a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.

Single-Perfect Blossom

17th-level Veilblade feature

You have mastered a technique for a single, undefendable strike aimed at a foe's weakest point. Once per turn, immediately after you deal your Sneak Attack damage to a creature that has fewer than half of its hit points remaining, you can use a bonus action to make a special melee weapon attack against the same creature. If the attack hits, it is a critical hit. You can apply your Sneak Attack on this critical hit, even if you have already used it this turn.
Once you make a successful attack in this way, you can't use it again until you finish a short or long rest.

Additionally, you can attempt to hide as part of your Fallen Petal feature.