Requires

Fury Storm must be in hand. Witherbloom Apprentice must be on the battlefield. You have cast your commander from your command zone this game. An additional instant or sorcery in hand with the mana to cast it, or an opponent has cast an as of yet unresolved instant or sorcery spell. Mana needed:

Steps

1. Cast your additional instant or sorcery spell, or wait for an opponent to cast one.
2. Witherbloom Apprentice triggers, losing each opponent 1 life and gaining you 1 life.
3. Cast Fury Storm targeting the instant or sorcery spell.
4. Witherbloom Apprentice triggers, losing each opponent 1 life and gaining you 1 life.
5. Fury Storm triggers, copying itself for each time you have cast your commander from your command zone this game and choosing the original copy of Fury Storm as the target.
6. Witherbloom Apprentice triggers for each copy, losing each opponent 1 life and gaining you 1 life each time.
7. Resolve a Fury Storm copy, copying Fury Storm and choosing the original Fury Storm as the target.
8. Witherbloom Apprentice triggers, losing each opponent 1 life and gaining you 1 life.
9. Repeat from step 7.

Results