Requires

Steps

1. Cast the additional instant or sorcery by paying its mana cost.
2. If Adaptive Training Post had two charge counters on it, it triggers, putting a charge counter on it.
3. Holding priority, activate Adaptive Training Post by removing three charge counters from it, copying the next instant or sorcery spell you cast this turn.
4. Cast Reverberate by paying its mana cost, targeting the spell cast in step 1.
5. Adaptive Training Post triggers, copying Reverberate, with the copy targeting the original Reverberate.
6. Resolve the copy of Reverberate, copying the original Reverberate, with the copy targeting the original Reverberate.
7. Repeat step 5.

Results