Sewer Demons of the Hilt

The Royal Academy of Engineers and the University of Requiem along with the local spellcasting population are known to produce a lot of magic, and failed spells aren't uncommon. Though the city of the Hilt itself has its streets and campuses checked for Silverbloom infestation, it's believed the sewers are not. 
The sewers and various tunnels running under the city are always a hub for strange rumours and myths, but a popular one in recent years is that Silverbloom has infested portions of the sewers underneath the streets and has caused a thin place to begin to form over the years, with demons popping in and out. 
People claim to say strange things darting under the grates and manhole covers, and that if an animal or child is left unattended by a grate they'll be dragged down by the demonic population. 
Requiem claims that this rumour is just a rumour, and that the sewers are checked for Silverbloom consistently, and some botanists have even come out to tell that Silverbloom requires much more sunlight than is given by the tunnels. That has not stopped people from theorising and fearing. 
This was substantiated when the Talon Band Axe Beaks caught the "Sewer Fiend", a summoned demon using the sewer as his base of operations. The Axe Breaks have said that no Silverbloom was located within the area that they caught the demon.