These black fissures are the result of staring into them.
The Deep Sea Council is already a relatively "clean" place. Lindong walks all the way from the direction of the manor; the residents of Ophira have formed temporary defense teams but ultimately cannot resist the invasion of shadows, even their prized steam carriages have been corroded, growing writhing black tendrils that fire "shells" into the crowd.
Anyone affected by them will instantly be swallowed by shadows, becoming assimilated into twisted darkness.
Under such an offensive, the residents' defense line becomes increasingly fragile; comrades who stood shoulder to shoulder one moment, turn into monsters lunging at them the next. Total collapse is only a matter of time.
And killing these shadow creatures is meaningless.