Pyromancer's Goggles, and Return the Favor

Prerequisites

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

Steps

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

Results

• Infinite magecraft triggers