"While you quickly scan for an escape route, one of the creatures reveals a strange fat cylinder. The creature twists off one end of the cylinder exposing a set of dark pustulated lips within. As you try to dive out of the way, a huge glob of slime suddenly bursts forth from that awful pair of lips. The glob hits you straight on and you find yourself engulfed by the sticky slime and pinned against a wall. You struggle vainly to escape and just as the slime invades your nose and your mouth and you begin to pass out, you see a dark form swim past, inside the ooze."
Built by the Mi-Go with the benefit of some knowledge bestowed unto them by Shub-Niggurath, the womb-cylinder is the birth chamber of a nasty burrowing parasite. The resourceful Mi-Go used this cylinder, its occupant and the ooze in which the occupant resides as a heavy-duty weapon for defending themselves against flying Mythos enemies. Now that humans have developed such military devices as full-automatic weapons, helicopters and planes, the Mi-Go occasionally employ this weapon against people, when the shit hits the fan.
a) Increased nastiness: the ooze is acidic, is toxic, is flammable, ignites on contact with air, or is protomatter
b) Decreased lethality: The cylinder only fires if it detects movement against its field of vision. Of course, standing perfectly still when surrounded by the horrors of the Mythos is pretty tough. Someone might be able to make it discharge before it gets pointed at them though, by tossing something through its field of vision.
This is from the Ice Cave.