Fist of Suns

Artifact

You may pay rather than pay the mana cost for spells that you cast.

2004-12-01:
This is an alternative cost to cast a spell.
2004-12-01:
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 {W}{U}{B}{R}{G}. Likewise, you can’t pay {W}{U}{B}{R}{G} to cast a creature with morph face down.
2004-12-01:
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).
2014-02-01:
If you pay {W}{U}{B}{R}{G} rather than pay the mana cost of a spell with {X} in its mana cost, the only legal choice for X is 0.