The Lightning's Blade clan was one of the many that inhabited Draenor, and was left behind by the Horde during its conquest of Azeroth. After the war, Ner'zhul attempted to reforge the Horde with a promise of new worlds, and managed to attain the partial loyalty of the Lightning's Blade. It has strong ties to both the Blackrock and Thunderlord clans.Template:Cite
Trivia
The game manual for Warcraft II: Beyond the Dark Portal refers to the Lightning's Blade Clan as an ally of the Thunderlord Clan during the Second War. Nothing more wasis known about the clan besides this. Some fans believed that the clan's name was simply a mistake, and that the intended reference was to either the Twilight's Hammer Clan or the Burning Blade Clan. However, one of the World of Warcraft Realms is named Lightning's Blade, clearly implying that the clan does exist, or existed at one time. In recent Warcraft novels such as Beyond the Dark Portal, however, the Lightning's Blade is confirmed to exist, and served Ner'zhul's Horde.
Source
BlizzPlanet World of Warcraft Server Realm Names Lore