The following is a short story intended as a campaign riff.
The adventurers stumbled through the rain. They were almost back to the ancient Crossroads Inn, the closest thing that seemed like civilization. The bard mumbled feverishly, "The stories say there has been an inn at this spot for over a thousand years. It was built to commemorate..." he didn't finish the sentence, but he didn't stop breathing yet, either.
The gate opened when they shouted and pounded on it, and the stableboy slammed it shut behind them. Soggy travelers looked at them, and then went back to their poor meals and watered beer. The roof leaked, and the low fire smoked and spit. It didn't do much to drive away the chill, but it was better than outside. The poor young priest who joined the party to try and gain the favor of his god and a better position in his temple went to work, and did the best he could with hot water, herbs, and a needle and thread. He thought he might be able to save the bard, but gut wounds were tricky things. The magician, the oldest of the four, ordered whiskey and lit a pipe with shaking hands. He'd thought so highly of his few magics, thought that surely his education and wisdom would help his comrades prevail. It all had gone so wrong...
The warrior looked at the battered gauntlets covering his hands. He had killed several, exulted in the feel of shedding blows from his armor. It had accomplished nothing. The enemy had outflanked them. He couldn't cut through them fast enough, and the magician's spells couldn't staunch the flow of screaming humanoids. He spoke loudly, too stunned to be certain who to address. "We couldn't save her. The Orcs were too many. We were too late. The girl...is gone."
The innkeeper nodded. They'd been hired right in front of him. The mayor from a tiny hamlet had come all the way here with a tiny bag of shining golden coins to find these men, the armed wanderers that stopped from time to time. "I'll send word to the family. Next few farmers going to the duke's market. They'll hear of it. You needn't stay. Nobody expects you to tell them yourself. I'll say you came back sore hurt, everyone will know you did your best." He knew they had been an unlikely gamble. They were too green, and the world was grown too dark. It always was. Still, he considered, it was fortunate that it had happened a few days ago. Not today. Any day but today. One day every ten years, the inn must be open from dawn to midnight. It had been explained to him on his father's knee. Every curse must have an out, for there could never be a perfect prison in the world. They must open the inn, day after day, and on those special days they could only pray that certain things did not come to pass.
The warrior kept talking. "The money they paid us...I don't want it anymore. I'd give it all up, if it'd change things."
The other band. The one in the back corner. The ones who had been coming here so, so long. One of them turned to look. "It's been a long time, my friends. Let us offer our services." His beard was long and ratty, matted. When he reached for his cup his fist was like a huge cudgel. Gnarled, scarred, solid-looking.
The one next to him was slender, with eyes that glittered out from beneath his deep black hood. "We were sworn. We cannot ask, nor seek." A third leaned forward on the table, deep black tattoos flowing up and down his forearms. His voice was like opening a trap door into a dusty, disused attic. "And yet no geas can be utterly binding. If the path is open, we may walk it and pass out of this prison. I sense that opening flowers before us."
The warrior cradled his face in his hands. "I want revenge! We were too weak, but there must be others." The barkeep had dropped his rag, and was speeding across the floor with hands outstretched, "Silence, sir! Speak no more, I beg you!" He knew the tale. It had been passed down from father to son, for generation upon generation. The inn must always stand, the binding must be undisturbed.
The warrior looked up at him with reddened yes, "And why shouldn't I give voice to what my heart says? My friend lies wounded unto death, and I want revenge!."
A hush fell over the bar. A crackle of something that couldn't be seen or heard or felt passed through the air, and the magician jumped as though he'd been pinched. "What is this? I sense old magic." The innkeep dashed forward, attempted to clamp his hand over the warrior's mouth, "You do not know! Please, listen, please! Do not offer them gold!"
The warrior stood and shoved the innkeep to the ground. "Don't dare to lay a hand on me! I've slain greater men for less. And I would give all the gold I have, if it would avenge what I have seen this day. I cannot rest until we are free from this scourge of orcs, though my strength is not enough-"
A shadow fell upon him, and the magician gasped. "Something has broken."
The warrior turned, and saw the cloaked figures from the shadowed corner. They seemed somehow brighter now. More present. Before they had been hard to attend to, but now they demanded his attention. He could not look away.
"Our price is not so high." An aged hand extended. Old, but still living, blood pulsing beneath the scarred flesh. Still strong. "One single coin of gold is our fee, but it must be gold no matter how small it might be. Such are the ancient ways, old already when we kept the contract. Gold for blood, a pact made under the roof of an inn. And this one is at a crossroads, besides. Even the Gods must respect a contract, if it be made at a crossroads. So it is, so it must be."
The innkeeper grabbed at the warrior's knees, "Do not do it! It will all start again! Some powers were better left alone!" The tattooed man snapped his fingers, and solid ice three inches thick snapped into place around the barkeep. He was frozen solid, and if he yet lived there was no sign of it. "No interference! If this man would be our client, we have the right to accept his bond and give our pledge." The magician paled. The energy required for such a spell was beyond him, beyond his master, beyond his master's master. He knew of no one who could accomplish such a thing.
The whole tavern held its breath. Woodenly the warrior took one shining yellow coin, and put it in the hand that waited for it. Five cloaked figures, as different as the forest from the mountains, or the sea from the desert, cast off their motheaten cloaks.
"After twelve centuries, we shall ride again." Ancient weapons gleamed, flawless as the day they came forth from enchanted forges. "The old tales will be remembered." Life and youth flowed back into the five, as they stood straighter. Their hair darkened, their skin shed wrinkles for heartiness, though the scars remained. A man who seemed now to have the muscles of an ogre tucked a single gold coin into a pouch at his waist. "We accept your quest. You shall have your revenge. They will die. All of them."
The five walked out of the inn and disappeared into the rain and darkness. Drops of water glistened on the block of ice surrounding the barkeep.
That night, thunder split the sky like the screaming of the gods. The next night, great fires could be seen on the mountains. On the third, bands of orcs with terrified eyes fled through. They slashed madly at those who stood in their way, but did not slow even to steal food. On the fourth, the king's knights rode through. They apologized to the innkeeper, but still they put his inn to the torch. A thousand orcs had died. Their tales had reached the tribes. War was brewing. The Five rode once more, with blades and sorcery that had not been known since ancient days. Men not even the gods could kill, men who had written themselves into the very bedrock of the universe, laughed at time and mortality, built legends and burned empires. They had found their way back from their long-forgotten half-life, resurrected by gold and revenge.
The stories had come to life. The dragons stirred in deep caverns that had been beyond the ken of men. Monsters yawned in the utterest darkness. Demons in forgotten places felt their bindings loosen. Young men and women pushed against their limits, and felt those limits give before them. The Heroes had returned, a new Age of Heroes dawned.
The gods wept, and the earth quavered in its bones at memories of blood and fire. It was all happening again.