Maerlyn's Rainbow
Maerlyn's Rainbow, which some call the Wizard's Rainbow, is a set of glass balls out of old legend, each one a colour of the rainbow.
Maerlyn's Rainbow is said to number thirteen pieces, one apiece for the Twelve Guardians and one more standing for the nexus-point of the Beams. The black piece goes by the name Thirteen. There are fireside tales about it, and an old warning that talking about Thirteen at all is unwise, since it might hear its name and roll toward the speaker.
The pink piece is Maerlyn's Grapefruit, and its glow seems alive to those who watch it, and hungry. Pieces like these, by one account, never stay long in one place or in one owner's hands.
How far into The Dark Tower have you read?
Set your place and this page rewrites itself to exactly that point. Nothing ahead of you will show.