For this group, the Tithe River certainly has 2 mouths.
The first was invisible. The Hidden Mouth, as the villagers called it, had some kind of field-effect active-comouflage bullshit that seriously screwed even with Hasver and Takir. Not to mention, of course, Simon: vanished into the river in the dark, miracles and all.
They engaged the creature with fire, mud, blasts of focused mind power, the debilitating doom contained in the future and the past, and ultimately: a doom laser. Finally, the thing was consumed in hungry green flame that ate chitin, fat, organs, and even bone in its grisly green dance (note to Roz: beware the Doom Laser).
Suluku came to praise them. Rhotia came to help Hasver after he collapsed from his wounds and exertion. The man was showing his age, and during treatment they saw how the synth side of him was growing in to replace fleshy portions burned by the plasma fire from the Doom Laser.
They rested for the night. They perused the floating houses, arguing from their own strengths and understandings. They chose one, and fitted it out a bit for floating with extra lily-pad analogues, and poles for poling, and food, and a portable brazier, and their trepidation.
The might of the Tithe bore them across Navarene, and into the depths of the Steadfast.
They found evidence of a sky-based weapon used by (presumably) the Gaian’s to destroy (and leave lingering negative effects in) the large port on the Tithe, and later, the remnants of the floating trade caravan they may have been on. Whatever the weapon was, it turned people into shadows, and ate substance, and left a stain in metal and stone – but not glass.
The river turned up its volume. Cliffs rose around it. In the gathering darkness they were powerless to escape the boat without great danger to themelves.
A long, long night of spinning and poling away from cliffs wore them down into exhausted sleep.
In the morning, they woke to find the river a pale mirror of the gorgeous heavens, spreading out seemingly to infinity.
They had reached the Sea of Secrets.
By the gulls wheeling overhead to the south, and the vague smell of pulp and vinegar, they knew: they had found Harmuth, or something quite like it anyhow….