Putrid Goblin, First Day of Class, and Carrion Feeder

Prerequisites

• Putrid Goblin on the battlefield
• First Day of Class in hand
• Carrion Feeder on the battlefield
• available

Steps

1. Cast First Day of Class by paying , causing all creatures that enter the battlefield under your control this turn to get an additional +1/+1 counter put on it
2. Activate Carrion Feeder by sacrificing Putrid Goblin
3. Putrid Goblin's persist ability triggers, returning itself from your graveyard to the battlefield with a -1/-1 counter on it
4. Putrid Goblin enters the battlefield, triggering First Day of Class, putting a +1/+1 counter on Putrid Goblin
5. Resolve the Carrion Feeder ability from step 2, putting a +1/+1 counter on it
6. Repeat from step 2

Results

• Infinite +1/+1 counters on Carrion Feeder
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers