Grindstone

Artifact    (CMC:1)

, : Target player puts the top two cards of his or her library into his or her graveyard. If both cards share a color, repeat this process.

"Memory is a burden that wears at the soul as weather wears at stone." —Crovax

223 TPR • ENGreg Simanson

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Legal in: Tempest Block,Legacy,Vintage,Commander

Oracle Text (click to copy):

10/4/2004
If the two cards are both colorless, then the effect does not repeat. It only repeats if both cards have at least one color and at least one color is shared between them.
10/4/2004
The effect repeats as many times as it takes to meet the end condition.