Dualcaster Mage, Black Sun's Twilight, and Ashnod's Altar

Prerequisites

• Dualcaster Mage in hand
• Black Sun's Twilight in hand
• Ashnod's Altar on the battlefield
• available

Steps

1. Cast Black Sun's Twilight by paying , optionally choosing to target a creature
2. Holding priority, cast Dualcaster Mage by paying
3. When Dualcaster Mage enters the battlefield, it triggers, copying Black Sun's Twilight, optionally choosing to target a creature
4. Holding priority, activate Ashnod's Altar by sacrificing Dualcaster Mage, adding
5. Resolve the copy of Black Sun's Twilight, giving up to one creature -5/-5 until end of turn and returning Dualcaster Mage from your graveyard to the battlefield
6. Repeat from step 3

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite colorless mana
• Infinite magecraft triggers
• Reduce any number of target creatures' toughness to zero