Mikaeus, the Unhallowed, and Devoted Druid

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Devoted Druid on the battlefield

Steps

1. Activate Devoted Druid's second ability by putting a -1/-1 counter on it, untapping it
2. Repeat step 1 until Devoted Druid dies as a state-based action due to having zero toughness
3. Devoted Druid dies, triggering its undying ability, returning it from your graveyard to the battlefield with a +1/+1 counter on it
4. Repeat

Results

• Infinite death triggers
• Infinite ETB
• Infinite LTB