Evolution Witness, Thran Vigil, and Putrid Imp

Prerequisites

• Evolution Witness on the battlefield
• Thran Vigil on the battlefield
• Putrid Imp on the battlefield
• You have a creature or artifact card in your graveyard
• You have a way to put a +1/+1 counter on Evolution Witness

Steps

1. Put a +1/+1 counter on Evolution Witness
2. Evolution Witness triggers, returning an artifact or creature card from your graveyard to your hand
3. Thran Vigil triggers
4. Holding priority, activate Putrid Imp by discarding an artifact or creature card
5. Resolve the Thran Vigil ability, putting a +1/+1 counter on Evolution Witness
6. Repeat from step 2

Results

• Infinite self-discard triggers
• Infinite +1/+1 counters on Evolution Witness