The Ur-Dragon, Haakon, Stromgald Scourge, Morophon, the Boundless, and Nameless Inversion

Prerequisites

• The Ur-Dragon on the battlefield or in the command zone
• Haakon, Stromgald Scourge on the battlefield
• Morophon, the Boundless on the battlefield
• Nameless Inversion in hand or in the graveyard

Steps

1. Cast Nameless Inversion from your graveyard, as it is a Knight card, by paying due to The Ur-Dragon and Morophon, giving a creature +3/-3 until end of turn
2. If the creature has toughness 0 or less, the creature dies as a state-based action
3. Repeat as desired

Results

• Reduce any number of target creatures' toughness to zero
• Reduce any creature's toughness to zero when it enters the battlefield