Rebecca Horne placed shards of an ancient crystal believed to be the Methuselah's Stone in the care of her many students. The powers of these crystals are legendary. When brought together are said to make an Immortal invincible.
Euterpe: Crystals do not count toward your Pre-Game limit. You may play this card if you have Calliope in play. During deck construction, you may either substitute any 1 non-Special Attack for 1 Basic Attack or substitute any 1 Defense for 1 Basic Block for each Crystal associated with your deck. Do not remove these Attacks and Defenses from the game if the Crystals leave play. You may only have 1 Euterpe in play.