Adamantium

Adamantium was a durable substance.

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)

An undercover agent posing as Beltempest dreamed of an event where he used an industrial blaster with a beam focus to cut a door-sized hole into an adamantium wall. (PROSE: Original Sin) Roz Forrester once tried to kick in the rotting wooden door to a 16th century church that served as Dantalion's lair. It had a hidden adamantium core which left her leg feeling like it was on fire. (PROSE: Original Sin)

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 to Wolverine's skeleton and claws.