Cheapest priced copy (Khans of Tarkir): $13.99 at Card Kingdom, near mint, their price list as of .
Altar of the Brood 
Artifact · Rare · Secret Lair Countdown · #1
Whenever another permanent you control enters, each opponent mills a card.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $13.99 to $69.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Khans of Tarkir | 216 | Rare | $13.99 | $15.99 |
| Secret Lair Countdown | 1 | Rare | $13.99 | $17.99 |
| Secret Lair Countdown | 28 | Rare | — | $69.99 |
| Ugin's Fate | 216 | Rare | $42.99 | — |
One ruling from Wizards of the Coast
- 20 September 2014If Altar of the Brood enters the battlefield under your control at the same time as other permanents, its ability will trigger for each of those permanents.