Before Markesh Prelin was replaced by an Usilar Prelin on the Aquali Throne there were other crises in the Barcelasian Empire. The late second millennia saw the Barcelasian Empire contract several times. This adventure can be placed in one of those contractions.
Polosita would be best placed north and east of Hamokera. There may be a few Barcelasians left, but it is now mostly manned by Usilar (humans) left behind when the main Barcelasian force was recalled. It is under attack by Saulabar (goblins). The player characters should probably be Usilar, but could also be Barcelasian.
Prince Seneal is a Barcelasian, a tall, powerful lizard-like creature, the ruling race of this world. Condurat might be a Barcelasian, or she might be a loyal Usilar. In the latter case, her loyalty, if successful, may well be part of the sequence of events that eventually led to an Usilar on the throne a few centuries later.
Why would Usilar stay in a Barcelasian fort? Many of the Usilar have assimilated into the empire, and have sworn to uphold it. It also is probably the safest place in the area: bandits do roam the countryside, after all. Their fields will be nearby, and with trade routes closing down they could starve without their crops. It may be that no one was expecting on attack on Polosita, that the Saulabar here were scattered and unaggressive towards the inhabitants, but some event triggered either an invasion or a more aggressive stance.