Lucky charm

Lucky charms are the life gaining artifacts in the Alpha (set); Crystal Rod, Iron Star, Ivory Cup, Throne of Bone and Wooden Sphere. They were printed in every Core Set through 8th Edition. The original lucky charms for white read:
Whenever a player plays a white spell, you may pay . If you do, you gain 1 life.

Their improved versions came out in Darksteel; Angel's Feather, Demon's Horn, Dragon's Claw, Kraken's Eye and Wurm's Tooth and they have been printed in every core set afterwards.

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.