The Bellerophon was an old Excalibur-class DropShip owned and operated until at least 3067 by the mercenary unit known as The Medusans. The Bellerophon was the flagship of Rear Admiral David Beatty, the commanding officer of Basilisk Assault Squadron, as well as the lead ship of the First Division within that squadron, with Commodore Trevylyan Naper serving as commanding officer of the First Division and XO to Rear Admiral Beatty. The second ship within the First Division was the Marksman, a Fortress-class DropShip.
At some point prior to 3068 the Bellerophon was converted into the Pocket WarShip configuration of the Excalibur-class; it was in fact one of the initial batch of seven ships to receive this upgrade before the upgrade program was cancelled, only to be reopened in 3068. The Bellerophon would use its increased weapon payload to noticeable effect during the attempt made by the Medusans to block the Capellan Confederation strike on New Syrtis in 3069. Having used a slingshot maneuver around New Syrtis to propel the Medusans' two assault squadrons into position to launch a deep space ambush against the Capellans, the plan devised by Admiral John Jellicoe saw both squadrons conduct a fast, slashing attack at the Capellan task force. The first warning the Capellans had was when missiles from the Bellerophon's Kraken-T launchers struck a pair of Capellan Union-class DropShips.
The Medusans managed to destroy a Leopard and a Triumph and damaged a number of other Capellan DropShips, but took damage in turn from the Capellan forces led by the Impavido class WarShip CCS Zhejiang, which was escorting the strike force. The Bellerophon took damage that left her main drive in need of a complete overhaul, and with the Word of Blake destroying shipyards across the Inner Sphere as the Jihad intensified the Bellerophon was still waiting for that overhaul in late 3071.
With the Medusans having taken heavy damage in combat throughout the Capellan March, rumors were circulating in late 3071 that Admiral Jellicoe was negotiating with other independent mercenary DropShips with a view to making good the Medusans' losses or possibly expanding the Medusans to include a third squadron. One of the ships apparently showing an interest in the proposal was the Thunderchild, sister-ship to the Bellerophon.
- Mercenaries Supplemental II, p. 51, "Basilisk Assault Squadron: Winning The Staring Match"
- Jihad Hot Spots: 3070, pp. 139, 140
- Mercenaries Supplemental Update, p. 90, "Medusans"