Ashaya, Soul of the Wild, Darksteel Garrison, and Barrenton Medic

Prerequisites

• Ashaya, Soul of the Wild on the battlefield
• Darksteel Garrison on the battlefield
• Barrenton Medic on the battlefield
• Barrenton Medic does not have summoning sickness
• Darksteel Garrison attached to Barrenton Medic

Steps

1. Activate Barrenton Medic by tapping it, adding
2. Darksteel Garrison triggers, giving Barrenton Medic +1/+1 until end of turn
3. Activate Barrenton Medic's second ability by putting a -1/-1 counter on it, untapping it
4. Repeat

Results

• Infinite -1/-1 counters on Barrenton Medic
• Infinite green mana