If Wondrous Labyrinth {*} stadium is in play, how many energy are needed for energyless attacks?

Any attacks that normally cost no energy now require at least one energy to be attached when Wondrous Labyrinth {*} is in play. However, if an effect like Persian's "Gathering of Cats" Ability sets an attack's cost to zero energy, Wondrous Labyrinth {*} does not add an additional energy requirement to it.

Relevant cards

SM9_158