When General Kerensky left the Inner Sphere in 2784, he took complete copies of the Star League's data cores, which included design specifications on every piece of military hardware ever proposed to the SLDF for production.
By the twenty-ninth century, Clan warriors all over the Kerensky Cluster were clamoring for newer, more capable BattleMech designs. Clan Mongoose scientists, interested in cutting development time, looked to the Star League memory cores in hopes of finding a design that would suit their needs. What they found was a BattleMech submitted for trials in 2753, one that has become nearly ubiquitous in the Inner Sphere – the Dragon.
The Mongoose scientists converted the design into the Great Wyrm, and the results were astounding. Production models entered service just over a year after the design process began. Though Mongoose scientists heavily modified the chassis they selected, making the Great Wyrm fifteen tons lighter than the Dragon, they managed to keep the same speed profile while increasing the firepower. Their only sacrifice was in overall armor protection; the Great Wyrm mounts 30 percent less armor than its parent design, a sacrifice deemed acceptable by its designers.
The remainder of the Golden Century was not so kind to the Great Wyrm. With the introduction of the OmniMech, many Clans quickly relegated the Wyrm to solahma units. Main production halted in 2869 after the Smoke Jaguars absorbed Clan Mongoose. Clan Burrock made several limited production runs in 2871 and 2872 after they captured a former Mongoose assembly plant on Foster, but Clan Fire Mandrill subsequently seized and retooled that facility. Since then, no new Great Wyrms have been built.

Source: Technical Readout 3060
Armament:
1 LRM-10 Launcher
2 GAA-22 Rapid-Fire Cannon
2 ER Medium Lasers
2 ER Small Lasers