Ashaya, Soul of the Wild, Darksteel Garrison, and Devoted Druid

Prerequisites

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

Steps

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

Results

• Infinite -1/-1 counters on Devoted Druid
• Infinite green mana