Finally some creature art!
This one has a back full of egg sacks, covered with bacteria and white slime.
These eggs form constantly in large amounts, even growing on each other. Each egg has an offspring growing inside and when it is fully formed - the egg detaches from the carrier and drops down, taking together other eggs that were holding onto it. Even if they were not fully formed yet. The whole process is just a mess.
Born infant breaks through from the membrane of the egg and following it's first instinct - eats it and the rest of the fallen egg sacks. After few hours the infant is able to hunt on it's own, as they develop and grow very rapidly.
These creatures are hostile towards anyone and hunt on sight. They prefer living in dark, cold and moist places. Your basement would be a perfect habitat