Ethersworn Canonist‘s ability prevents players from playing more than one non-artifact spell per turn. This limitation applies to playing spells via alternate means; such as Cascade or Hideaway. Even the triggered ability of Knowledge Pool can be interfered with by the Canonist’s ability. With Ethersworn Canonist and Knowledge Pool in play, if a player casts a non-artifact spell they would be prevented from casting a different non-artifact spell that has been removed by Knowledge Pool.