Karne, Grand Magister

Karne costs {1} less to cast for each Crystal on the
battlefield. This can also be applied to the colored
cost.
Eminence - Whenever you cast another creature
spell, if Karne is in the command zone or on the
battlefield, you may pay {2}. If you do, create a
colorless artifact token named 'Crystal' with
"{t}: Add one mana of any color."