None of the two sisters registers as evil.
They head over to the room. Before they even get to the locked trap door, you can hear loud banging and screaming from a woman from it. "Open up already! Open up! I swear you will regret it if you don't open up IMMEDIATELY!"
Katya glances back worriedly, but eventually her greed for the promised coins wins out. She works on the lock and steps back just in time to escape the flashing silver dagger of Lusica. The guardswoman looks terrible, insomniac, panicked and with burn marks and soot disgracing her wardrobe, hair and skin. Lucy's acting like a caged animal and not paying much attention to you as she stabs after the wild-eyed little maid.
Behind her, one of the tall Red Guard cohorts very slowly climbs up the ladder leading up and out of the trap door. He too looks to be in terrible shape, with stiff limb movements and a wide gash in his side. The wound is heavily swollen, with a suspicious clear liquid dripping from it.
In the darkness under them, you can hear something
very large sniffing, growling animalistically and prowling around. From the sounds of it, it would be way, way, waaay too large and heavy to fit through the narrow shaft, even less so climb up the flimsy ladder. At least you hope so.
The guardsman has been wounded with giant wasp poison, a weapon poison that stiffens the affected and can in severe cases even cause paralysis. (Injury, Fortitude DC 14, initial and secondary damage 1d6 Dex)
The sounds like they come from a feline predator, although much too loud and guttural, and also strangely warped, almost as if they were human... or formerly human.