Pyromancer's Goggles, and Expansion // Explosion

Prerequisites

• Pyromancer's Goggles on the battlefield
• Expansion // Explosion in hand
• plus enough mana to cast the additional instant or sorcery available

Steps

1. Cast any instant or sorcery with mana value 4 or less by paying its mana cost
2. Holding priority, activate Pyromancer's Goggles by tapping it, adding
3. Cast Expansion by paying its mana cost, targeting the instant or sorcery cast in step 1
4. Pyromancer's Goggles triggers, copying Expansion, with the copy targeting the original Expansion
5. Resolve the copy of Expansion, creating a copy of Expansion targeting the original Expansion
6. Repeat step 5

Results

• Infinite magecraft triggers