Cheapest priced copy (Commander Legends: Battle for Baldur's Gate): $0.79 at Card Kingdom, near mint, their price list as of .
Curtains' Call 
Instant · Rare · Commander Legends: Battle for Baldur's Gate · #746
Undaunted (This spell costs {1} less to cast for each opponent.)
Destroy two target creatures.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
5 printings · $0.79 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2016 | 13 | Rare | $1.49 | — |
| Commander Legends: Battle for Baldur's Gate | 746 | Rare | $0.79 | — |
| Commander Masters | 146 | Rare | $0.99 | $1.99 |
| Commander Masters | 506 | Rare | — | — |
| Outlaws of Thunder Junction Commander | 130 | Rare | $1.49 | — |
3 rulings from Wizards of the Coast
- 8 November 2016You can't cast Curtains' Call without two creatures to target. If one becomes an illegal target after you've cast Curtains' Call, the other will still be destroyed.
- 8 November 2016Causing an opponent to lose the game after you've announced that you're casting a spell with undaunted and determined its total cost won't cause you to have to pay more mana.
- 8 November 2016Effects that reduce what you pay to cast a spell don't affect its mana value.