Adamantium

Adamantium was a type of metal.

The Crown of Sherak was placed into an adamantium casket. While possessing Siobhan Sadler, the Diadem attempted to place itself into an adamantium vacuum case to avoid destruction. (PROSE: Legacy)

The Adamantium was a ship of the the Consortium, a mineral mining organisation. (PROSE: Fear of the Dark)

Behind the scenes
Adamantium is a fictional alloy that originated in Marvel Comics, notably being bonded Wolverine's skeleton and claws.