Discarded bike lock key
From A KoL Wiki
Locking your bike up seems extreme. All you really need to do to keep it from wandering off is tie its reins to a post with a simple quick-release knot, like a double half-hitch or something.
Look, I'm still pretending this is a medieval fantasy game, okay
Type: accessory
Cannot be traded or discarded
Quest ItemMaximum MP +10
Regenerate 4-5 MP per adventure
(In-game plural not known - currently impossible to determine.)