I created a very small world (next one up from pocket), large enough to only support two mega-beasts. So it started off as the age of the Hydra and the Savanna Titan. There was a mountain range in the north, another in the south and the two were separated by a vast swath of swampland that easily took 3 days to cross. There were only two human civilizations present on the world, clustered roughly around each of the mountain ranges. The dwarves only survived about 350 out of 550 years of history. They were killed by one of two elvish civilizations that existed far to the north. There were also two kobold civilizations, and a single goblin tower.
I started off an adventurer like normal. While I could've picked a dwarf to play, it didn't fit the flavor the world had established. So I played a human swordsman named Jalew Noblepetal. I'd get quests to go off and kill bandits of various stripes. Axemen, macemen. Humans and goblins. Exciting times, and I built up a bit of a reputation in the world. My forays into the great swamp were always exciting and involved me dashing off to a monster lair I had cleared out (or thought I had) just as the sun was setting, and holing up for the night. It's actually kinda exciting to know that if you get caught outside at night alone, there's a good chance that you're not going to see the sun again.
Anyway, I worked my way through all of the regular quests and was eventually directed to go and talk with a lady in her castle. So I trekked to the castle and talked with her. She wanted me to kill the Hydra that had been plaguing the land since time immemorial. I gathered up a posse and headed to the cave where the great beast was holed up. While it managed to kill off about half of my band, we took it down. I even got the killing blow in. Went back to the lady to report. She was pleased to hear the news of the creature's death but she said that my task was not yet done. I was to take down the Titan next.
Well, I replenished my numbers from the soldiers stationed in her castle (they were more than eager to join with the great hero of the land). Upon stepping outside the castle walls though, we were ambushed by a warband of goblins, and I lost more than a dozen of my travelling companions. I went back to the castle and recruited some more, as apparently there were dark forces in the world that wished to see me fail at my task.
With my party back at full, I made my way south, through the trackless swampland. Because of where the castle was positioned, the trek through the swamp took a full four days, during which time I was ambushed another two times by kobolds. With only three companions left out of an initial party of 19, I stopped at another castle and recruited some more. With more eager recruits in tow, I set forth on the final leg of my journey.
The titan, whose name was Fima Rockspacked the Windy Splash of Tulips, was keeping watch over an ancient temple. My group and I charged in to face the being, whose body was formed from the blackest opal and who sported two long tails trailing out behind it. The battle didn't last long. I forget who finally get the final killing blow in. A swordsman, I think. But we all had a hand in Fima's death. I returned back to the castle and let the lady know of my success. I retired to a small town just outside of the castle.
When I started up a fortress, I did it on the remains of the titan's temple, and a further story sprang into my head. The dwarves had been banished by the combined power of the hydra and the titan, and locked away by seals maintained by the titan. Upon the titan's death, the seals weakened and broke. This makes a sort of sense, given that when I started the fortress, the world passed into the Age of Fairy Tales. If I find myself inclined, I might write up the full story and pull all of the cool bits of world history into it.