Mighty Mutanimals + Devoted Druid + Hapatra, Vizier of Poisons

Mighty Mutanimals

Devoted Druid

Hapatra, Vizier of Poisons

How it works

1. Activate Devoted Druid's first ability by tapping it.
2. Activate Devoted Druid's second ability by putting a -1/-1 counter on it.
3. Hapatra triggers, creating a creature token.
4. When the creature token enters, Mighty Mutanimals triggers, putting a +1/+1 counter on Devoted Druid.
5. Resolve the Devoted Druid ability from step 2, untapping it.
6. Repeat.