Gloom Scout

Gloom Scouts excel at slinking around in the shadows: in sewer networks and back alleys of large cities, or in caves and subterranean passages. They are fearless explorers of the dark, confident in their ability to spot any potential threats and also that they can stay hidden from any potential threat. They do venture forth onto the surface and into the light of day, but they feel exposed and vulnerable without the protection of the darkness.

Get the Drop

At 3rd level, you know that the best way to strike in combat is first. You have advantage on Initiative rolls and you can give yourself a bonus to your initiative rolls equal to your Wisdom modifier.

Umbral Sight

At 3rd level, you gain darkvision out to a range of 60 feet. If you already have darkvision from your race, its range increases by 30 feet.

You are also adept at evading creatures that rely on darkvision. While in darkness, you are invisible to any creature that relies on darkvision to see you in that darkness.

Slink Through Shadows

At 9th level, you have learned to flit from shadow to shadow to find an unexpected angle from which to strike your target. When you are in dim light or darkness, as a bonus action you can teleport up to 60 ft. to an unoccupied space you can see that is also in dim light or darkness. Your first weapon attack then scores a critical hit on a roll of 19 or 20 until the end of your turn.

Opportunist

Starting at 13th level,  felling your foes creates an opening and you know how to take advantage of the effect gravity can have on a fresh corpse.  

The first time you reduce a creature to 0 hitpoints on your turn, you can take a free action. That action can be used only to take the Attack (one weapon Attack only), Dash, Disengage, Hide, or Use an Object action.

Stalker's Flurry

At 17th level, you learn to attack with such unexpected speed that you can turn a miss into another strike.

Once on each of your turns when you miss with a weapon attack, you can make another weapon attack as part of the same action.