Devoted Druid, and Quillspike

Prerequisites

• Devoted Druid on the battlefield
• Quillspike on the battlefield
• Devoted Druid does not have summoning sickness

Steps

1. Activate Devoted Druid's first ability by tapping it, adding
2. Activate Devoted Druid's second ability by putting a -1/-1 counter on it, untapping itself
3. Activate Quillspike by paying and removing a -1/-1 counter from Devoted Druid, giving Quillspike +3/+3 until end of turn
4. Repeat

Results

• Infinitely large Quillspike until end of turn