Rite of Passage + Mirage Mirror + Walking Ballista

Rite of Passage

Mirage Mirror

Walking Ballista

How it works

1. Activate Mirage Mirror by paying 2, causing it to become a copy of Rite of Passage until end of turn.
2. Activate Walking Ballista by removing a +1/+1 counter from it, dealing 1 damage to itself.
3. Rite of Passage and Mirage Mirror trigger, putting two +1/+1 counters on Walking Ballista.
4. Repeat from step 2 an arbitrarily large number of times.
5. Move to the next turn, removing all damage marked on Walking Ballista.
6. Activate Walking Ballista by removing a +1/+1 counter from it, dealing 1 damage to any target.
7. Repeat step 6 as desired.