GBA Nature Ring

From Zelda Wiki.org

The GBA Nature Ring is found in the secret GBA shop in Horon Village. The shop is only available in Oracle of Seasons, when the cartridge is played on a Game Boy Advance. This ring does nothing when worn, absolutely nothing. Never keep it in a Ring Box. Never wear it. Just acquire it on your way to obtain all sixty-four Magic Rings.

This could be considered the Oracle of Seasons version of the GBA Time Ring.