Devil

Devil is a steel sword found in The Witcher 2. So far I've found it on the Mysterious Merchant in Act 2 Iorveth's Path. I've also seen reports of a Diagram available from the asylum in Act 1: 14x Iron Ore 2x Leather 2x Timber 2x Essence of Death 4x Essence of Water

http://en.thewitcher.com/forum/index.php?/topic/30004-diagram-devil/ is the only other thing I could find about Devil, besides another wiki with no info.