You may payrather than pay the mana cost for spells that you cast.
12/1/2004 This is an alternative cost to cast a spell.
12/1/2004 You can’t pay more than one alternative cost for a spell. For example, you can’t cast a spell using its flashback ability by paying . Likewise, you can’t pay to cast a creature with morph face down.
12/1/2004 Note that combining this card with Mycosynth Lattice from the Darksteel set means that all spells can be cast for five mana of any type (colored or colorless).
2/1/2014 If you pay rather than pay the mana cost of a spell with in its mana cost, the only legal choice for X is 0.