Logic Knot

Instant, XUU (2)
Delve (You may remove any number of cards in your graveyard from the game as you play this spell. It costs {1} less to play for each card removed this way.)
Counter target spell unless its controller pays {X}.¹
Illus. Glen Angus

Crystal Keep Rulings Summaries

• You can cast this with X equal to zero, but it's not generally useful to do so. [D'Angelo 2007/05/15]
• Note - Also see Delve, Rule 502.64.
• Note - Also see X Costs, Rule G24.1.

Format Legality	Legal in Vintage, Legacy, Extended Banned in Standard
Printings (1/9)	Future Sight (Common)