Heartstone | Magic: The Gathering
Formats Heartstone is Legal in
Official Oracle Text for Heartstone
Official Rulings for Heartstone
10/4/2004 : It will not add a to abilities with no generic mana in their activation cost.
10/4/2004 : It will never reduce any colored mana portion of an activation cost.
7/15/2006 : Can't reduce Snow mana costs.
7/1/2013 : Activated abilities contain a colon. They're generally written "[Cost]: [Effect]." Some keywords are activated abilities; they have colons in their reminder text.