Note: This tale is based on SCP-1440, and it is better read after reading that article.

The old man woke, and his failures flooded his mind once more. The destruction of the Foundation base was just another drop in an ocean of guilt. Sometimes, he didn't know what still kept him afloat, what stopped him from drowning in the depths of despair and madness, from simply ceasing to care about the race he could so easily destroy. Perhaps it was nothing more than simple spite, the dying memory of defiance against his tormentors. It did not matter much.
The desert he found himself in was a lonely, empty place, and for that he was glad. Out here, he could do little harm. He started walking towards a distant chain of mountains, driven by a compulsion he learned long ago he could not resist. Once, he would throw himself into deep gorges, into rivers, into the sea, hoping the elements could keep him from causing any more damage, but the Brothers were stronger even than them. He would lie in depths of the earth, thinking he could finally rest in the dark, only to blink and find himself in the world above once more, making his way towards humanity like the bearer of a plague. The Brothers were nothing if not persistent.
As the soft desert sand crunched beneath his feet, he remembered that thrice accursed game of cards that led to all of this, to the three follies that sealed his fate.
First came the game: he should have never challenged them, he should have known better. But he was young, and full of pride, and had much to lose. He was a man in his prime when he lost his life in a meaningless war, and found himself in the Brothers' dark halls. Around him, his fellow soldiers walked silently towards the distant light, not even glancing at the three gaunt figures that showed them the way. But not he. He could not accept his fate. He had a young, pretty wife, a prospering farm, he could not lose it all, would not. He thought the others were fools, weaklings, to accept their demise thus. In his vanity, he challenged his guides, and refused to go forward until he was given the chance to fight. He got his chance, and he won. He won too much.
Second came his greed: the Brothers could not have known how good he was. He took every hand, broke every gambit, stole life from Death's grasp with guile and skill. The Brothers were displeased, but they accepted their defeat, and showed him the door back to the world of the living. As he stood at the exit, he suddenly thought, why stop now? He was the best card player to ever live, he could have it all! Why settle for life when he could have glory, power, immortality! He turned and sat back at the table. "Double or nothing", he said. And he won again. And again. And again. The Brothers were less gracious now, but still, they admitted their defeat. Three prizes he won from them: the cup, the cards, and the sack. They were the Brothers' prized possessions, and they offered him much if he would only return them: wealth, and luck, and health, and glory, but he wanted to humiliate them, to make Death grovel before him. So he took the prizes and left the Brothers seething in rage. He would pay dearly for his vanity.
Third came the waste: the prizes were items of immense power, for they could keep the Brothers at bay: the First's cup held the elixir of life, and a drop of it would banish him, saving even the sickest of men from his grasp. Every time he saw the Small Death lurking behind the shoulders of a man, he would sprinkle a drop towards him, and the First would flee, cursing and spitting. A drop seemed like such a small thing, and the cup held so much water, so he used it carelessly. He banished the First from those too old or frail to keep on living, from those the First rightfully owned. And eventually, the cup ran dry. When his wife began wasting away from the consuming illness, he had no water left for her. The First sneered as he took her away.
The prize of the Second was greater, like the Second himself. With the cards, he could challenge the Second's authority, hold the power of the Great Death at bay. When war was brewing, when man turned against his brother, he was there, to challenge the Second, to turn the tides of fire and steel. But like the waters of life, the cards of fate were wasted- he used them for every border skirmish, every civil dispute, every growing revolution, and the cards became more worn with every passing use. Though they lasted for longer than the water, eventually the Second refused to heed their call. He watched the world plummet into wars greater than he could ever imagine, watched millions die for nothing in the mud, watched the innocent suffer and bleed and burn. The Second laughed when he took them away.
The prize of the Third was the greatest. The sack of the All-Death could hold anything within it, contain even the greatest catastrophes, stop even the most dire forces from ever releasing their fury upon the earth. With the sack, he curbed the fury of storms, drowned fires that threatened to consume entire cities, held creatures most unnatural and fell, whose origin was not of this world. The sack held longest of all the treasures, but it too grew weak- its seams could not hold such mighty powers forever. He used the sack as foolishly as he used the lesser treasures- he stopped storms that would have passed, held fires that could have been contained. His sin was greater than mere wastefulness, though. The sack still held one last use, could hold one last being. In his search for the Third he saw the forces of darkness grow ever stronger, saw brave men and women like those of the Foundation risk their lives in order to contain them. Yet, he would not spare the last use of his sack. It was all he had left, his final hope. He knew the only way he could force the Third to release him from his endless torment was to capture him in the sack, and thus force him and his brothers to let him die. The All-Death never appeared, though, not even to mock him. When the forces of the unknown claimed a victim, only silence greeted them.
Once the prizes ran out, the true horror of his fate became apparent. The Brothers feared him no longer, and did not forgive his vanity, his wastefulness, his lording over Death. They wanted him to suffer, and death was far too good for him. Instead, he brought death upon everyone else- forced to seek the Third forever, and to watch humanity crumble in his wake. His curse, like his follies, was triple- never to die, always to seek, always to destroy.
The mountains grew closer and closer, and the old man allowed himself a moment of rest. His compulsion could be controlled, if but for a short while. He sat down in the sand and turned his gaze upwards, towards the stars. In the dark blue, early morning sky, only a few remained, but they shined brightly and cleanly. Looking at them, the old man remembered why he kept his head above the water. Perhaps this was the greatest of his follies, but it was one he was willing to allow himself. The world was too beautiful for him to allow its destruction without a fight, and humanity deserved better than to perish because of the mistakes of a foolish old man. He could not stop himself from hurting them, but he could give them one thing- his hope. He would stop himself, even at the price of oblivion.