Prismari, the Inspiration, and Return the Favor

Prerequisites

• Prismari, the Inspiration on the battlefield
• Return the Favor in hand
• available

Steps

1. Cast any other instant or sorcery by paying its mana cost
2. Holding priority, cast Return the Favor by paying its mana cost, targeting the instant or sorcery cast in step 1
3. Return the Favor's storm ability triggers, creating at least one copy of Return the Favor targeting the original Return the Favor
4. Resolve a copy of Return the Favor, copying Return the Favor targeting the original Return the Favor
5. Repeat step 4

Results

• Infinite magecraft triggers