Cheapest priced copy (Magic Origins): $2.49 at Card Kingdom, near mint, their price list as of .
Sphinx's Tutelage 
Enchantment · Uncommon · The List · #ORI-76
Whenever you draw a card, target opponent mills two cards. If two nonland cards that share a color were milled this way, repeat this process.
{5}{U}: Draw a card, then discard a card.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $2.49 to $14.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Magic Origins | 76 | Uncommon | $2.49 | $5.99 |
| The List | ORI-76 | Uncommon | $2.79 | — |
| Special Guests | 75 | Mythic | $7.49 | $14.99 |
2 rulings from Wizards of the Coast
- 22 June 2015The process will keep repeating as long as both cards share a color and neither is a land card.
- 22 June 2015Colorless is not a color, so putting two colorless cards into a graveyard won’t cause the process to repeat.