Call to Glory in exile (exiled by Isochron Scepter).
Isochron Scepter and Tezzeret's Touch on the battlefield.
Tezzeret's Touch attached to Isochron Scepter.
You control creatures that can tap to produce at least ({3} magic symbol) .
Steps
Activate creatures you control by tapping those, adding ({3} magic symbol) .
Activate Isochron Scepter by paying ({2} magic symbol) and tapping it, casting a copy of Call to Glory without paying its mana cost, untapping all creatures.