Logic Knot

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

Gatherer Card Rulings [Nov 2009]

• 5/1/2007: Using delve doesn't reduce the value of X. It just reduces the amount of mana Logic Knot's controller has to pay.

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