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

Prerequisites

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Steps

1. 1Cast 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. 2If the creature has toughness 0 or less, the creature dies as a state-based action.
3. 3Repeat as desired.

Effects

• Reduce the toughness of creatures opponents control to 0
• Reduce the toughness of each creature opponents control to 0 upon entering