Moon Pearl

The Moon Pearl is a shining gem which allows Link to retain his normal form while in the Dark World. Other humans entering are transformed into forms which reflect their "True Nature". This is shown by the pair of men on Death Mountain, as well as Link himself. The bully is transformed into a demon-like creature because of his devilish nature, and the other man turned into a ball because he could never make up his mind. Link's "true nature" is aparently a cute little pink bunny rabbit, probably due to his kindness and compassion. The Pearl appears in A Link To The Past.