Pilot was conjoined to the Leviathan, Moya, a living, biomechanoid ship by the Peacekeeper's who killed the former pilot in turn for one that would cooperate with their plans. Pilot agreed and was artificially conjoined to Moya until he disconnected himself from the Peacekeeper implants, beggining anew to the five cycle process of natural bonding. The project was to use Moya to create a Leviathan warship. After a seal had been broken by D'Argo, Moya became pregnant with such a Leviathan, Talyn.
Talyn prematurely starbursts away from Moya with Craise on board as his "captain". Moya is frantic to find him and eventually does so. However, Talyn is frightened and untrusting even to Crais who has accepted a "hand of friendship" with Talyn.
As Talyn is periodically away Moya and Pilot have a wide variety of experiences with the crew. Despite the Peacekeeper attempts at creating a warship out of a Leviathan, they have no weapons at all. Their only form of defense is starburst, where they jaunt or warp into space and push out to the other side of space. Starburst can easily "jump" a Leviathan through space but is still apparently not as fast as a Scarran dredgenaut can travel.
As well as very often having Pilot as a conjoined being, Leviathan's accomodate themselves to being able to host a ship crew. They will change as they grow to suit the crew's convenience and needs. Much of a Leviathan's maintenance is taken care of by the Drd's who also generate as a Leviathan grows.