According to Velinde's Journal, the Lords of the Emerald Flame are an incredibly powerful enemy of the worgen. They do battle with the worgen on their native homeworld, and Velinde Starsong got to know of this ferocious war through her use of the Scythe of Elune. Apparently, the struggle against the Lords of the Emerald Flame does not go too well, as the worgen found their enemy to be an unflinching one indeed. "Emerald Flame" may refer to "fel", meaning that the Lords of the Emerald Flame are part of the Burning Legion or their minions/warlocks.