Arcanite Skeleton Key

Overview
The Arcanite Skeleton Key can be used by Blacksmiths to open locked doors or chests requiring up to 300 Lockpicking skill.

This includes all Eastern Kingdoms and Kalimdor chests, as well as Bound Fel Iron Chests, but excludes Bound Adamantite Chests. It also includes the locked doors in all instances in Eastern Kingdoms and Kalimdor, but none in Outland or Northrend.

Source
This item is crafted with Blacksmithing (275).