Cheapest priced copy (Modern Horizons 2): $1.49 at Card Kingdom, foil, near mint, their price list as of .
Sanctum Prelate 
Creature — Human Cleric · 2/2 · Mythic · Secret Lair Drop · #278
As this creature enters, choose a number.
Noncreature spells with mana value equal to the chosen number can't be cast.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
3 printings · $1.49 to $8.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Conspiracy: Take the Crown | 23 | Mythic | $2.99Out of stock | $8.99 |
| Modern Horizons 2 | 491 | Mythic | — | $1.49 |
| Secret Lair Drop | 278 | Mythic | $6.49 | $4.99Out of stock |
2 rulings from Wizards of the Coast
- 23 August 2016For spells with {X} in their mana costs, use the value chosen for X to determine if the spell's mana value is the chosen number. For example, if the chosen number is 4, a noncreature spell with mana cost {X}{R}{R} couldn't be cast with X equal to 2, but it could be cast with X equal to any other number.
- 23 August 2016Effects that increase or reduce the cost to cast a spell don't affect that spell's mana value.