Once, high on a hill where the clouds sat down to rest, a small unicorn named Otis was polishing the rainbow.

Swish, swish, swish went his soft cloth along the red stripe. He buffed the orange until it glowed like a peach. He rubbed the blue until it sparkled like a puddle in sunshine. Otis was the Rainbow Guard, and every morning he climbed the hill to make sure all seven colors shone bright for the whole valley below.

"Good morning, rainbow," he said, tapping it gently with his silver horn. "You look wonderful today."

But that morning, something was wrong.

The purple stripe was gone.

Otis blinked. He walked all the way to the end of the rainbow and back again. Red, orange, yellow, green, blue, indigo... and then nothing. Just a pale, empty space where purple should have been, like a missing tooth.

Otis felt worried. His chest went tight and fluttery, like a little bird was hopping around inside it.

Then he heard it. *THUD. THUD. THUD.*

Footsteps. Enormous ones. Otis peeked over the edge of the cloud and saw three giants walking away through the forest below. They were as tall as barns, with mossy hair and knobbly knees. And the tallest one carried a jar under her arm — a jar full of swirling, glowing purple.

"Stop!" Otis shouted. But the giants were already gone, and his voice was very small.

Otis sat down. He thought hard. Guards protect things, he told himself. So I will protect the rainbow.