Otherworldly Patron: The Umbral Lurker

Warlocks who make a pact with the Umbral Lurker gain control over shadows and darkness itself by authoring a deal with the nightmares that live in the shadows of the deep, dark places of the world. Entities such as Lloth and Strahd are capable of entering umbral lurker pacts with mortals, issuing their dark powers to worthy vessels. A warlock with this pact can be a dark practitioner without remorse, a noble soul treading a troubled path with purpose, or a mischievous trickster with the night on their side.

Special Mechanics:

• The ability to manipulate shadows in a wide variety of ways. Also: the ability to conjure a shadow pony.
  
• Servant of Darkness: See in the dark, turn out the lights! Improves existing darkvision.
  
• Living Shadows: Have your shadow friends eat your enemies, and spit them out elsewhere.
  
• Shadow Prison: Lock someone down in darkness and do some damage. Does on average twice the removal of Hurl Through Hell, but 60% of the damage.

Balance Concerns:

• Not technically a concern with balance, but warlocks can take the Misty Visions invocation to cast silent image at will, and silent image is also on the spell list here. The invocation is still viable, though, because casting silent image off the spell list requires a spell slot, but is easier for the warlock to access without investing in an invocation.
  
• Living Shadows gives a ribbon (fluff ability) in addition to its crunchy ability, unlike other warlock level 6's, but I'm pretty sure that's alright. The ability overall is balanced like a reversed Misty Escape that potentially deals damage and a condition, but is harder to use because it requires a save and you being in dim light or darkness.
  
• Shadow Prison is intended to be a midway point between Hurl Through Hell and Dark Delirium, and it functions very similar to such. However Dark Delirium is a short-rest power and Shadow Prison is a long-rest, so Shadow Prison has the possibility of being very slightly underpowered for what it is. 

Version 0.5

Link to the reddit thread.