Spitemare, and Fiendlash

Prerequisites

• Spitemare on the battlefield
• Fiendlash on the battlefield
• Fiendlash attached to Spitemare
• You have a way to give Spitemare indestructible
• You have a way to deal damage to Spitemare

Steps

1. Give Spitemare indestructible by any method
2. Deal damage to Spitemare
3. Fiendlash and Spitemare trigger
4. Resolve the Fiendlash trigger, dealing at least 5 damage to any player or planeswalker
5. Resolve the Spitemare trigger, dealing at least 1 damage to itself
6. Repeat from step 3

Results

• Infinite damage