Little is known about the combat skin other than that it was used by infantry personnel. It is comparable to the Mjolnir Armor but far more advanced. While guiding John-117 through the Library, 343 Guilty Spark questioned the use of "such ineffective weapons" to combat the Flood. He notes that the MJOLNIR is ill-suited to combat the Flood, and recommends that he upgrade to a Class 12 Combat Skin from the MJOLNIR, which is ranked on the Forerunner classification system as a Class 2. On the other hand, Guilty Spark also notes that the MJOLNIR will serve John well when the Flood begins converting Halo's atmosphere, commenting that he is a "good planner." Upon learning that there was a powered armor system six times more powerful than the MJOLNIR, John expressed enthusiasm at the opportunity t