Mikaeus, the Unhallowed, Defiant Greatmaw, and Viscera Seer

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Defiant Greatmaw on the battlefield
• Viscera Seer on the battlefield
• Defiant Greatmaw does not have a +1/+1 counter on it

Steps

1. Activate Viscera Seer by sacrificing Defiant Greatmaw
2. When Defiant Greatmaw dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
3. When Defiant Greatmaw enters the battlefield, its first ability triggers, putting two -1/-1 counters on it
4. Defiant Greatmaw's second ability triggers, removing a -1/-1 counter from another creature you control
5. Resolve the Viscera Seer ability from step 1, causing you to scry 1
6. Repeat

Results

• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers
• Infinite scry 1