Myr Welder, Umbral Mantle, and Five Hundred Year Diary

Prerequisites

• Myr Welder on the battlefield
• Umbral Mantle on the battlefield
• Five Hundred Year Diary in exile

Steps

1. Activate Myr Welder using Five Hundred Year Diary's ability by tapping it, adding at least Activate Myr Welder by paying and untapping it, giving it +2/+2 until end of turn
2. Repeat

Results

• Infinite untap of creatures you control
• Infinite mana creatures you control can produce
• Infinitely large creature until end of turn
• Infinite blue mana