"The noble work of our order is to infuse all life on Esper with etherium. Our goal will be reached more rapidly if new life is ... suppressed."

Ethersworn Canonist

Each player who has cast a nonartifact spell this turn can't cast additional nonartifact spells.

"The noble work of our order is to infuse all life on Esper with etherium. Our goal will be reached more rapidly if new life is . . . suppressed."

Mystery Booster 2

Double Masters

Modern Masters

Magic Online Theme Decks

Shards of Alara

Each player who has played a nonartifact spell this turn can't play additional nonartifact spells.

Each turn, each player can cast any number of artifact spells plus a maximum of one nonartifact spell.

Ethersworn Canonist takes into account spells that were cast earlier in the turn before Ethersworn Canonist entered the battlefield, including any spells that are somehow still on the stack. However, any spells on the stack as Ethersworn Canonist enters the battlefield have already been cast by that point, so they're not affected by it.