Any device or artefact generated by or powered with magic, regardless of the magics alignment. Furthermore it needs to be unique or otherwise indestructable. Otherwise it is merely a magical device.
“A magical artefact is a device or artefact respectively that is powered with magic. It can be...Magical Artefact
“The Ginzuishou, or Silver Crystal, is a very powerful magical artefact which can generate Light...Ginzuishou