House says, "Now, even if those implants were made of adamantium..." referring to the fictional metal first mentioned in Avengers #66 (1969). Additionally, it is all but indestructible, the second-hardest substance in the Marvel Universe. Several lesser forms of adamantium are less expensive and easier to forge but are also less durable. Adamantium is best known as the substance merged with Wolverine's bones and claws.