After Clan Hell's Horses invaded Clan Wolf's Inner Sphere territory, the Horses needed to rebuild from the losses they incurred. A surprising partnership with Clan Wolf-in-Exile led to the Cygnus, which entered service in 3075. Based on the Annihilator, the simple design of the Cygnus allows for fewer things to go wrong without losing its lethality. A possible reflection of this design philosophy is that the ammo feed tracks are situated outside of the hull feeding from shoulder bins, while this has not so far been proven to be a vulnerability the design may have been chosen to improve feed reliability. It is a BattleMech, rather than an OmniMech, the decision of a desperate Clan that needed to rebuild as quickly as possible.
The Cygnus is swift for a 'Mech of its size, as its 380 engine makes it capable of 64 km/h, though that comes at an increased vulnerability due to the bulk of the XL Engine. An Endo Steel chassis also saves weight. [Source: sarna]
You can download the papercraft model here: Classic BattleTech - Cygnus Free Mech Paper Model Download