User blog comment:Mcgee1095/Are all the floating island chests locked?/@comment-69.165.137.160-20111027023215

All floating island chests are indeed locked. All dungeon gold chests (not brown) are locked. All shadow chests in the Underworld are locked. The difference between a locked Gold Chest and locked Shadow Chest, is that Gold Keys are one-time uses, where Shadow Keys are infinite use. Gold Keys are found as rare drops from any monster in the Dungeon, guaranteed drop from the Dungeon Slime (it has a key floating in it), and, at least in my experience, guaranteed to show up in any brown chest found in the Dungeon. Shadow Keys can be found in the locked Gold Chests in the Dungeon. You only need to worry about keeping one of those though.