Take the tour ×  Normally, when you cast a spell without paying
its mana cost, the {X} in its mana cost is 0.  Mind Grind,
however, has an additional restriction:  Mind Grind  X can't be
0.  Clearly you can't choose for {X} to be zero when you cast it
normally. But what happens if you don't get to choose, e.g. when
you cascade into Mind Grind or cast it with Epic Experiment?
share|improve this question Curious, why the need for the X
can't be 0 restriction? It seems like if that weren't there, and
you did cast it for x=0, then each opponent simply wouldn't have
to reveal any cards, because they have already "revealed 0 land
cards". So it would be a pointless, wasted spell... why the
additional restriction? –  GendoIkari Jan 31 at 13:30
@Gendolkari I think the restriction is there because the card
would be confusing without it. The card says "Each opponent
reveals cards from the top of his or her library until…" If X is
0 do they still reveal the top card? Rewording the instructions
to be clear is harder than