Here are two moveset options, ordered from best to worst:
- Sleep and Kill: Leftovers
Dark Void: Puts the foe to Sleep, allowing for Bad Dreams to destroy.
Dark Pulse: Good power, high accuracy, STAB, decent chance to cause flinching, type coverage is good.
Taunt: Stops the foe from using Sleep Talk and other non-attacking moves, including Taunt.
Calm Mind: The foe is usually going to switch once put to Sleep, so you can use that time to raise your stats.
- Standard Darkrai Set: Leftovers/Big Root
Dark Void: Puts the foe to Sleep, allowing for Bad Dreams and Dream Eater if you have it.
Dark Pulse: Good power, high accuracy, STAB, decent chance to cause flinching.
Embargo: Stops the use of hold items.
Dream Eater/Spacial Rend/Roar of Time: Dream Eater works well with Dark Void, heals Darkrai, has high accuracy, high power, and deals with Fighting types. Spacial Rend and Roar of Time are moves that only the movie givaway Darkrai has. Spacial Rend has high power, decent accuracy, and a good chance for a critical hit. Roar of Time has high power and decent accuracy. The advantage of Roar of Time is that while your foe is asleep, they won't be able to attack you on the turn after Roar of Time when you are recharging.