- "A single fighter with a four-to-one kill ratio, shields, and a variable weapons payload are odds you are willing to bet on, Captain? Return to base now - those Marines are already gone."
- ―Colonel J Isaev
The SX-class Seraph, designated the Type-31 exoatmospheric multirole fighter, is one of the main space fighters in service with the Covenant Empire. Introduced to supplement and replace the Gigas-pattern fighter-bomber and Tarasque-pattern heavy fighter, the Seraph became one of the most common aircraft adopted by the Covenant, second in abundance only to the CSX-class Banshee. It is widely regarded as being the one of the most effective aircraft ever designed by the Covenant, spawning numerous design patterns to fulfil nearly every role imaginable.
Finding adoption among select Covenant fleets during the Human-Covenant War, the Duvan Nu-pattern bomber, nicknamed by the UNSC as the Cerastes, is a heavily-armed mutation of the Kai-pattern fighter. Introduced fairly late into the Covenant's history, it is intended to fill the hole for a dedicated bomber in the Covenant's formidable fighter arsenal. While not held within as high regard as other fighters, their ability to change the course of entire ground campaigns have given their pilots a sense of smugness not seen outside of the bomber division.
The two-man Cerastes is built with an emphasis on speed, and is capable of keeping pace with other Covenant space fighters. This is due to a number of factors, namely a larger impulse drive and a thinner and smaller hull. It features a much more bulbous profile on a larger frame which allows it to carry extended magazines of oversized fuel rods, which are unleashed upon its targets from three rapidly-reloading bomb bays. Between all three, its entire payload can be delivered in under a minute. While this is already considered an impressive display of firepower, it can further bolster its attacks with a hardpoint for a dumbfired plasma torpedo or a heavy plasma cannon. Both of these weapon systems are mounted beneath it due to its intended use against ground targets, where it can perform devastating dive bombs preferred by Sangheili pilots. Unfortunately, its lack of a defensive anti-aircraft cannon and default shield generators leaves it vulnerable to interception, which is why they must be escorted into contested airspaces. It is also fairly short-ranged, as the speed it can fire off its entire payload and the limited space for fuel restricts the distance it can travel.
Because of these weaknesses, even after it entered mass-production in 2547 many Sangheili-dominated units opted to retain the Tarasque-pattern bomber, with those that used the Duvan Nu employing them as logistics craft. Instead, most of the new aircraft fell into the hands of the Jiralhanae, who appreciating its firepower, deployed them against both space and ground targets. Although rarely observed by the UNSC before-hand, their popularity exploded in the conflicts occurring during and after 2551 as the brutes became more widespread. With their numbers being decimated by the Great Schism, and Sangheili dismantling them, the Cerastes is currently only observed within brute holdouts.