Samuel Beechworth is thoroughly familiar with the Wrenhaven (the Heart claims that he "knows the River Wrenhaven and all its tributaries, down to the smallest inlet") and is employed by Farley Havelock to navigate it. Samuel reveals to Corvo that he has seen things of a strange and magical nature on the river, such as mysterious lights and faces in the water.
The river is also known for dispersing strange artifacts along the shore, such as runes and bone charms, which are believed to be the remains of an ancient city that once stood on the land Dunwall now occupies.
In the wake of the plague, many of the river's bridges are derelict and collapsing (with Kaldwin's Bridge standing as a notable exception). Many corpses are dumped into the river, with the resulting smell not being a pleasing one.