Rats have 50% conceal

[Egon the Monkey]

Unless the Sewer Rats are being used by Agatha for Imp Invis casting practice, I'm assuming this is a similar bug to the attempt to remove collision on the Keeper Swarms. Not a huge problem with them being non hostile, but rather wierd.

[Sion Ti'ren]

They also drop sinew, which noone picks up cluttering the area horrably and seems to stop any more from spawning.
 
EDIT: and Dire rats are rediculously weak, while the concealed "weak rats" arn't, which is a bit odd
 
EDIT2: The rats also seem noticably... unresponsive, and should probablys have there scripts checked.

[St Juste]

Sewer rats concealed 50% and friendly (not red)...