Mikaeus, the Unhallowed, Glen Elendra Archmage, and Bartolomé del Presidio

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Glen Elendra Archmage on the battlefield
• Bartolomé del Presidio on the battlefield

Steps

1. Activate Bartolomé del Presidio by sacrificing Glen Elendra Archmage
2. When Glen Elendra Archmage dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
3. Resolve the Bartolomé del Presidio ability
4. Activate Bartolomé del Presidio by sacrificing Glen Elendra Archmage
5. When Glen Elendra Archmage dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
6. Resolve the Bartolomé del Presidio ability
7. Repeat

Results

• Infinite +1/+1 counters on a creature
• Infinite ETB
• Infinite LTB
• Infinite death triggers
• Infinite sacrifice triggers