All overpowered random drop weapons are removed in the PC version and only present in the unpatched Xbox 360 version. This weapon does not exist on the PC Enhanced Version.
Devil is a steel sword in The Witcher 2: Assassins of Kings. There have been 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
Within the PC version, Devil is available from the "Mysterious merchant" within act 2, on Iorveth's path.