Cheapest priced copy (Mystery Booster 2): $4.49 at Card Kingdom, near mint, their price list as of .
Ethersworn Canonist 
Artifact Creature — Human Cleric · 2/2 · Rare · Shards of Alara · #10
Each player who has cast a nonartifact spell this turn can't cast additional nonartifact spells.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
5 printings · $4.49 to $29.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Double Masters | 14 | Rare | $5.49 | $5.99 |
| Shards of Alara | 10 | Rare | $5.49 | $29.99 |
| Mystery Booster 2 | 10 | Rare | $4.49 | — |
| Modern Masters | 14 | Rare | $5.49 | $8.99 |
| Secret Lair Drop | 2102 | Rare | $7.49 | $7.49 |
2 rulings from Wizards of the Coast
- 7 August 2020Ethersworn 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.
- 7 August 2020Each turn, each player can cast any number of artifact spells plus a maximum of one nonartifact spell.