The Deep Yuck is a parasitic organism of Rolara’s deep waters, attested in the flooded halls of the Sunken Temple of Tathra. It takes the form of a subtle, translucent film, faintly like algae, easily missed in dark water. Its danger lies precisely in how little it announces itself.
Effect
The Deep Yuck afflicts only creatures that breathe underwater. Once it takes hold it begins to smother its host, closing off the very breath it relies on the host to draw. The first signs are an itching and a dull ache near the point of contact; this gives way to a numbness that creeps outward into the limbs, regardless of where the film first made contact. Left unchecked, the affliction suffocates the host quickly.
Because the Deep Yuck is a living thing rather than a passive contagion, it can be confronted directly. Separating the host from the film, or destroying the organism outright, ends the threat. Both approaches are attested to work, and both require someone other than the afflicted host to act, since a smothering victim is in poor condition to do either.
Habitat
The Deep Yuck favors cold, lightless water. It has been recovered from a drowned body within the Temple, which suggests it colonizes the dead as readily as the living, taking root wherever water-breathing creatures come to grief beneath the surface.