Cheapest priced copy (Commander Masters): $1.49 at Card Kingdom, near mint, their price list as of .
Yennett, Cryptic Sovereign 
Legendary Creature — Sphinx · 3/5 · Rare · Commander Masters · #363
Flying, vigilance, menace
Whenever Yennett attacks, reveal the top card of your library. You may cast it without paying its mana cost if its mana value is odd. If you don't cast it, draw a card.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
5 printings · $1.49 to $2.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2018 | 51 | Mythic | — | $2.99 |
| Commander Masters | 363 | Rare | $1.49 | $2.49Out of stock |
| Commander Masters | 596 | Rare | — | — |
| Secret Lair Drop | 1019 | Mythic | — | — |
| Secret Lair Drop | 2121 | Mythic | — | — |
5 rulings from Wizards of the Coast
- 13 July 2018Because all attackers are chosen at once, a spell cast this way can't affect which creatures you can attack with, but it can affect which creatures will be able to block.
- 13 July 2018If the revealed card doesn't have an odd mana value or if that card does but you choose not to cast it, you draw a card. Keep in mind that revealing a card doesn't cause it to change zones. This means that the card you draw will be the card you revealed.
- 13 July 2018If a spell has {X} in its mana cost, you must choose 0 as the value of X if you cast it without paying its mana cost.
- 13 July 2018If you wish to cast the revealed card without paying its mana cost, you must cast it while Yennett's triggered ability is resolving; you can't cast for free it later in the turn.
- 13 July 2018If you cast a card "without paying its mana cost," you can't choose to cast it for any alternative costs, such as evoke costs. You can, however, pay additional costs. If the card has any mandatory additional costs, such as that of Tormenting Voice, those must be paid to cast it.