Tel'aran'rhiod

Instead of paying the casting cost of a spell
of any color, its caster can choose to discard
a card that shares a color with that spell. If a spell
has {x} in the casting cost, X is zero.
also known as the World of Dreams and the Wolf
Dream, is a parallel world where all the possibilities
of the Wheel of Time connect, and it is linked to all the myriad such worlds that exist within the Wheel.