Cheapest priced copy (The Brothers' War Retro Artifacts): $0.49 at Card Kingdom, near mint, their price list as of .
Keening Stone 
Artifact · Rare · Rise of the Eldrazi · #219
{5}, {T}: Target player mills X cards, where X is the number of cards in that player's graveyard.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
5 printings · $0.49 to $1.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Brothers' War Retro Artifacts | 26 | Rare | $0.49 | $0.49 |
| The Brothers' War Retro Artifacts | 89 | Rare | $0.49 | $0.79 |
| The Brothers' War Retro Artifacts | 89z | Rare | — | — |
| Commander 2016 | 259 | Rare | $0.69 | — |
| Rise of the Eldrazi | 219 | Rare | $0.69 | $1.49 |
One ruling from Wizards of the Coast
- 15 June 2010The value of X is determined as the ability starts to resolve. If the targeted player has five cards in their graveyard at that time, for example, this ability will put five more cards into that graveyard from the top of that player's library.