Elixir of Demonslaying

The Elixir of Demonslaying is an Alchemy-made potion that enhances attack power by 105 against demons.

Source
The Elixir of Demonslaying is crafted by Alchemists with a skill level of 250.

The recipe is sold in limited quantity by the following NPCs:
 * Nina Lightbrew in Nethergarde Keep in Blasted Lands for the Alliance
 * Rartar in Stonard in Swamp of Sorrows for the Horde