Heartstone 
Artifact
Activated abilities of creatures cost 
less to activate. This effect can't reduce the mana in that cost to less than one mana.
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyLEGALvintageLEGALcommanderLEGAL
Artifact
Activated abilities of creatures cost less to activate. This effect can't reduce the mana in that cost to less than one mana.