Isochron Scepter and Animate Artifact on the battlefield.
Animate Artifact 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 To Arms! without paying its mana cost, untapping all creatures.