When the humans first began to flee the city, many of them insisted on the safety of their pets. An elite bunker intended for a previous world war made a serviceable compromise, and so as people sickened they left their cats locked deep underground. It was meant to be a generous act, a life-saving one - but when the humans deserted them entirely the cats remained trapped.

What has become of those ancestral kittypets is CavernClan. They are kept warm and unfettered in their bunker - powered by intact solar panes, they have lights and running water and a sprawling room with shelves full of canned food. The cats adapted to their isolation over the years, and learned that the highest precipice they had, the top stair of the master staircase, was a serviceable place to break open cans. This has become routine now, a gentle nudge sending a can to crack open on the cement below.

These cats rarely see live prey, and subsist on the canned and powdered food they have uncovered from the pantries. Descended from kittypets they are comfortable with the human food, though also keep a close eye on their distant sky lights. Built into the concave ceiling, the sky lights lurk hundreds of feet above even the master staircase, and sometimes emit unintended prey.

These animals rarely survive the fall, and even more infrequently is it another cat, usually an unlucky soul from LakeClan. CavernClan's elders remember stories of life aboveground inherited from parents and friends, and tell the kits hushed tales that have since faded to legend. Not even the youngest and most foolish kits believe that there are places such as this still existing, and view the few cats that fall to their deaths in their halls as fellow kittypet strays.