The Iron Pariah is a battleship that seems to be inhabited entirely by cats. Ezra and Cate see the ship ride by them while foraging for mushrooms in Act IV; the shrieks and wailing of cats can be heard well before the ship arrives on screen. Cate suggests that the Iron Pariah is rumored to have been a part of the Civil War. She also recounts a story of a friend of hers who accidentally encountered the ship while sailing, and found it to be eerily silent except for the sound of "mewing."
Shannon encounters a painter along the Echo River who exclusively paints shipwrecks, though he also has often attempted to sketch the Iron Pariah, but because of its elusiveness has had no luck in doing so.
The island on which Ezra and Cate pick mushrooms is a visual reference to the painting Isle Of The Dead, by Arnold Böcklin. The artist himself explained no meaning or provenance for the painting, but he did describe it as "a dream picture," and it is commonly interpreted as a stop on the River Styx.