Snow permanents you control can tap to produce at least ({3} magic symbol) .
({1} magic symbol) ({S} magic symbol) available.
Steps
Activate Rimefeather Owl by paying ({1} magic symbol) ({S} magic symbol) , putting an ice counter on Lithoform Engine, causing Lithoform Engine to become a snow permanent.
Move to your combat phase, and declare Jorn as an attacker, triggering its ability.
Holding priority, activate all mana producing snow permanents you control by tapping them, adding at least ({3} magic symbol) .
Activate Lithoform Engine's first ability by paying ({2} magic symbol) and tapping it, copying Jorn's triggered ability.
Resolve the copy of Jorn's ability, untapping all snow permanents you control.
Repeat from step 3.
Results
Infinite mana snow permanents you control can produce.