Cheapest priced copy (New Phyrexia): $0.35 at Card Kingdom, near mint, their price list as of .
Shrine of Limitless Power 
Artifact · Uncommon · New Phyrexia · #154
At the beginning of your upkeep and whenever you cast a black spell, put a charge counter on this artifact.
{4}, {T}, Sacrifice this artifact: Target player discards a card for each charge counter on this artifact.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| New Phyrexia | 154 | Uncommon | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 1 June 2011Unlike most abilities that force a player to discard cards, this ability may be activated whenever you could cast an instant, including during your opponent’s draw step after they have drawn a card.
- 1 June 2011You can’t force an opponent to discard a card they cast by activating the last ability in response. The spell is on the stack by then.