Haakon, Stromgald Scourge + Morophon, the Boundless + Nameless Inversion + Arcane Melee

Haakon, Stromgald Scourge

Morophon, the Boundless

Nameless Inversion

Arcane Melee

How it works

1. Cast Nameless Inversion from your graveyard, as it is a Knight card, by paying 0 due to Arcane Melee 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.

This loop relies on a brilliant alignment of cost reduction and graveyard casting: with Morophon, the Boundless naming "Knight" to eliminate the five colored mana symbols from tribal spells, and Arcane Melee chipping away at the remaining generic cost, your spells become completely free. That discount transforms Nameless Inversion—which has changeling and is therefore a Knight card—into a zero-cost removal spell you can continuously fire off. Because Haakon, Stromgald Scourge allows you to cast Knight spells directly from your graveyard, you can simply pull Nameless Inversion right back out of the bin each time it resolves, letting you repeatedly reduce the toughness of opposing creatures to zero without ever running out of ammo.