Zardazil

Zardazil was a rare soft-metal used to create alloyed weapons that were undetectable and could be easily "hidden inside" a person. Because of the unique properties of zardazil-alloy weapons, they could be phased within a person and carried under complete concealment.

Description
In its raw state, zardazil was an amber to red color, similar to raw iron in some respects. It was also rather soft for a metal but extremely durable.

Locations
This metal was scarce and in the mid–14th century DR, it was found only in mountains and mines around the Lake of Steam and in sandy fissures in the heart of the Raurin desert.

Uses
Any item partially or wholly composed of zardazil became intangible to the first being whose blood it spilled, similar to the ironguard spell. When this was done deliberately, it allowed a person to carry it without detection, typically attached to a non-metallic necklace. While it was in this state it did not harm the "carrier" and could not be affected by any spells such as heat metal or enlarge in an attempt to damage their person.

Ardrethra Laurindar, a professional slayer, as well as at least three Waterdhavian noble ladies were said to have used zardazil blades in this manner.