Hero's Cache is a side quest from The Legend of Zelda: Breath of the Wild. It is given to Link by Kass, who can be found at Kitano Bay. "My cache is at 17 of 24" refers to a 24-hour clock position where the north of the area corresponds to noon. The treasure can be found at 5 o'clock. There is a Gold Rupee in the Treasure Chest hidden between the rock in the 5 o'clock position and can be accessed by using the Magnesis Rune. Spoiler warning: Spoilers end here.