Urza, Lord High Artificer, Worldwalker Helm, and Echo Storm

Prerequisites

• Urza, Lord High Artificer on the battlefield
• Worldwalker Helm on the battlefield
• Echo Storm in hand

Steps

1. Cast Echo Storm by paying
2. Echo Storm triggers, copying it for each time you've cast your commander from the command zone this game
3. Resolve all Echo Storms, creating a token copy of Worldwalker Helm and a Map token for each Echo Storm
4. Activate Urza's first ability by tapping a Worldwaker Helm and a Map, adding
5. Activate a Worldwalker Helm by paying and tapping it, creating a token copy of the Worldwalker Helm token and a number of Map tokens equal to one plus the number of Worldwalker Helms you control as you resolve this ability
6. Activate Urza's first ability twice by tapping two Maps, adding
7. Repeat from step 5

Results

• Infinite blue mana
• Cast all cards in your library without paying their mana costs
• Infinite Map tokens
• Infinite Worldwalker Helm tokens
• Exile your library