Mikaeus, the Unhallowed, Pith Driller, and Sarcatog

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Pith Driller on the battlefield
• Sarcatog on the battlefield
• Pith Driller does not have a +1/+1 counter on it

Steps

1. Activate Sarcatog's second ability by sacrifiicing Pith Driller
2. When Pith Driller dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
3. When Pith Driller enters the battlefield, it triggers, putting a -1/-1 counter on it
4. Resolve the Sarcatog ability, giving it +1/+1 until end of turn
5. Repeat

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinitely large Sarcatog until end of turn