From Destinypedia, the Destiny wiki
Mercury Conquerors are elite Cabal units encountered in The Lighthouse Public Events on Mercury. They are survivors from The Almighty, and their goal is to gain control on the planet. When killed, they grant a little percentage increase to the Flashpoint milestone.
Mercury Conquerors are seen all around the Lighthouse, always spotted fighting with Mercury Defenders. They could be any Cabal from Legionaries to Incendiors to Colossi. They are usually distinguishable by their bright gold armor plated onto them. They are just like other of their kind, just with more health.
List of appearances