Chains of Mephistopheles and Bone Miser on the battlefield.
Two additional noncreature nonland cards in hand.
One additional card of any type in hand.
({3} magic symbol) ({B} magic symbol) available.
Steps
Cast Nightmare Void by paying ({3} magic symbol) ({B} magic symbol) , targeting yourself, discarding a noncreature nonland card.
Bone Miser's last ability triggers, causing you to attempt to draw a card.
Chain of Mephistopheles's replacement effect causes you to instead discard a card, then draw a card.
Resolve the ability, discarding a second noncreature nonland card, and using Nightmare Void's Dredge ability to mill two cards and return Nightmare Void from your graveyard to your hand instead of drawing.
Bone Miser's last ability triggers, attempting to cause you to draw a card.
Resolve this effect as before, discarding Nightmare Void, then milling two cards and returning Nightmare Void from your graveyard to your hand.
Repeat from step 5 until you have no cards in your library.
Discard any creature or land card to end the loop.