You gain automatic proficiency in the Stealth ability, allowing you to apply your proficiency bonus to your Stealth (DEX) Ability Checks

You gain a proficiency in the Languages Common and Infernal

You can see within darkness and dim light as if it were bright light, due to being a living shadow.

Radiant Damage, being essentially volatile and pure light, is very strong against you, as you are made of pure shadow. 

You gain a +1 bonus to your dexterity stat.

While standing in dim light or complete darkness, snapping your fingers will fuse you with the shadows. Your perception and movement will not be altered. Performing any action that affects another being will alert that being. If you are attempting to attack, you will have to reveal yourself from the shadows. This will count as a sneak attack if you are a Rogue.

While fused with the shadows in dim light, you can be seen using magic sight. In full darkness, you are imperceptible, even with magic. Detect magic will not detect you.
When merged with the shadows, stepping into bright light will cause you to be revealed, as well as dealing 3 points of damage. This also occurs when within 10ft of any explosion's damage radius, as well as within the affected area of any Light-based spell.
Taking 15 or more Radiant damage from any source, magical or nonmagical, while fused with the shadows will force you out of them, and you will need to take a short rest before you can enter the Shadows again.

You can move silently if you travel 1/3rd of your maximum movement speed, rounded down to multiples of 5. You are entirely unable to be heard when utilizing this trait