Lucky charm

Lucky charms are the life gaining artifacts first seen in Unlimited Crystal Rod, Iron Star, Ivory Cup, Throne of Bone and Wooden Sphere. They were printed in every Core Set since then until their improved versions came out in Darksteel; Angel's Feather, Demon's Horn, Dragon's Claw, Kraken's Eye and Wurm's Tooth

The original lucky charms for white read: Whenever a player plays a white spell, you may pay . If you do, you gain 1 life.

The version from Darksteel read: Whenever a player plays a white spell, you may gain 1 life.

The newer versions require no activation cost. They just cost more to cast.