Intruder Alarm, and Skirsdag High Priest

Prerequisites

• Intruder Alarm on the battlefield
• Skirsdag High Priest on the battlefield
• Skirsdag High Priest does not have summoning sickness
• You control at least two other untapped creatures
• A creature has died this turn

Steps

1. Activate Skirsdag High Priest by tapping it and two other creatures you control, creating a 5/5 Demon creature token
2. The Demon enters the battlefield, triggering Intruder Alarm, untapping all creatures
3. Repeat

Results

• Infinite creature tokens
• Infinite ETB
• Infinite mana creatures you control can produce
• Infinite untap of all creatures