The Helios-class Heavy Frigate is a light capital ship used by the UNSC for close escort and hunter-killer missions, and in a few cases, patrol duties. It is a modified variant of the Heimdall-class frigate, lacking the notable dorsal structure for carrying marine forces. Instead, it uses the power and space taken up by this to mount three deadly M54 Renegade Naval Support Guns. These guns carry two 350mm gauss cannons, capable of accelerating a large slug to one quarter of the speed of light, causing horrendous damage to a ship on impact. One such slug could cripple a unshielded SDV-class corvette. A entire battery can reduce a fully shielded SDV to smouldering wreck in just twenty seconds.