Dwarf Fortress mostly doesn’t have unique gameplay mechanics or anything; but the Legends viewer certainly is a unique feature, due to how all the systems work together to weave randomly generated stories and history of the world through the entire world generation process. So even though you didn’t play the game through all those years, the game still kept track of everything going on while simulating the world creation and you can go through it and see all the battles, conflicts, migrations, rise and fall of civilizations, deaths of monsters, etc.