Well , you have perhaps heard faerie-tales about a luck when you saw rainbow. Many people died when the rainbow shines upon them - but this faerie-tale is based on reality. Long time ago , when druids were stronger , they knew a great knowledge about nature, and discovered how they can increase luck of their friends. It needs a rainbow - of course, but it is not true that each rainbow increases luck. And how you can create rainbow? When it is raining and you cast this spell , rainbow will appear - you\'ll see.