The Lower Key is a key item that appears in Wario: Master of Disguise.
The Lower Key is a small blue key that appears to have a shape of a dolphin ghost at the end of it (fitting the location it is found in).
The Lower Key is one of two keys that can be found in Blowhole Castle with the other being the Upper Key. The Lower Key is located inside of a purple treasure chest in the center room being guarded by three Buffy the Dolphins. This key can be used to unlock a nearby door in a locked room that is dark.