Iron Whale

The Iron Whale was one of two submarines secretly appropriated by the Blue Frogs after the Koan Repbulic disbanded most of its navy. Using Thurmacc's friend and rival Gaius as an intermediary, they hired Thurmacc's crew to make modifications to the submarine to make it suitable for deep-sea combat and exploration.
However, Thurmacc's boss, Fortunio, used the Blue Frogs' funds and vessel toward his own ends, secretly converting the submarine into a rocket that could launch past the Rim in search of the Orphan Sphere. The Blue Frogs discovered the ruse too late, and with Thurmacc's help, Fortunio was able to launch the Iron Whale before Gaius could reclaim it.
The crew left Thurmacc behind in their rush to launch, realizing the slim probability of thier mission's success required someone to stay behind and continue their work. No one has heard from the Iron Whale since that fateful day. Perhaps its crew are dead, or perhaps they explore lands farther than any on the spheres have ever visited before.