All but one.
That one returned a final time. He was alone and his appearance unexpected. When all else was done, and Antrax was functioning as intended, the input receptors had been closed. No further instructions were necessary. Then the last creator appeared and opened the receptors anew. He gave greetings to Antrax. They could speak to each other through the keyboards and touch screens. They could communicate as equals. He told Antrax that the worst had come to pass. Everything was lost. The world was destroyed, and civilization was in ruins. Centuries of progress had been wiped out. Art, culture, knowledge, and understanding were gone. The creators, save he alone, were destroyed. Perhaps no one was still alive anywhere in the entire world. Perhaps everyone was dead.
Antrax did not respond. It had not been built to understand human emotion; it could not sense it in the words of the creator who spoke to it. But a new directive followed, and Antrax was required to obey directives. The directive entered its memory banks through the keyboard and became a part of its consciousness. The command was clear. Those chambers, the complex, and everything housed within had been given to Antrax to ward. They must not be compromised. They must not be lost. It was not enough that Antrax watch over them and keep them safe for when the creators returned. Antrax must protect them, as well; it must combat and destroy anything that threatened them. The means for doing so was already in place, weapons and defenses both, installed in secret by the last creator himself, who knew better than his fellows what the times required. Antrax must draw from its memory banks, as it did energy from its power cells, knowledge of how those defenses and weapons worked. It must adapt that knowledge to fulfill its directive; it must extrapolate what was needed to survive. If defenses or weapons were called for, Antrax must use them. If they were not enough and others were required, Antrax must build them. If anyone tried to reclaim the chambers without entering the proper code, the intrusion must be stopped-even at the cost of lives.
The final admonishment was a direct violation of any previous programming, but the command was overriding and absolute. Causing harm to humans was permissible. Killing was allowed. Antrax was given control over its own destiny. No one must threaten its existence or interfere with its purpose and function. No one must enter into its domain without knowledge of the code. That was the new directive. That was how Antrax was reprogrammed in the final throes of the apocalypse, when the last of the creators disappeared. It was alone for a long time after that. No one came to try to find it. No one even ventured close. In the ruins of the city, nothing moved. Not humans, animals, insects, or birds. The air was hazy and thick with debris, and nothing lived within its gloom. Antrax kept its vigil over the catacombs it had been set to guard. It warded them carefully, speeding down its lines of communication, through its myriad halls and chambers, into its memory banks and energy cells, all across its kingdom. Always watching. For a very long time, it had no need to do so; there was nothing outside to watch for. There was nothing but wasteland.
Sometimes, it wondered why it was guarding the underground chambers. It had been told what was housed there, but it did not understand why that held such importance for the creators. Some of it, yes. Some of it was obvious. Mostly, it was a puzzle. Antrax had been programmed to solve the puzzles that confronted it, and so it sought a solution to that one. It consulted its memory banks for help and got none. Its memory banks were vast, but the information stored there was not always useful. Words could be vague and confusing, especially when lacking a context into which to put them. Mathematics and engineering provided the most familiar and useful concepts, for Antrax had been built and programmed from them. Yet other words were only strings of symbols that meant nothing to it. Pictures and drawings confounded it. Vast amounts of the information it had been given seemed pointless, so much so that as its knowledge and sense of self-sufficiency grew, it even questioned the programming choices of the creators.
But the directive was immutable. Everything housed within the catacombs was precious. No part of it must be disturbed. No piece must be lost. Everything must be saved for when the creators came to reclaim it.
Yet when would that time come? Antrax had a vague memory of a blueprint for such a time, but the directive of the last creator had blurred and finally erased the specifics. There seemed to be no rules for when the catacombs should be opened up again. Or to whom. The catacombs it warded must be left inviolate, must be protected and preserved, must be kept hidden and safe.