My first experience with obsidian actually rather reminds me of how the aztecs must have felt. We had had our long war with the giant badgers, they were unparallelled in combat and possessed great ferocity the likes of which had never before been seen. The Fort itself was based atop a flat desert plain, with a river running through it giving the Fort life. Giant series of tunnels connected all the storage below the heat of the sun to the housing and the Fortress growing taller under the heat of the sun. My Dwarves - all clad in bone armour, holding bone weapons and obsidian swords felt invincible. I was sure that I was doing well, after all, I had heard well just how difficult DF was and it felt like I was overcoming something brutal and challenging, that I was winning against DF's odds. Once I had discovered that giant badgers would flee from our hounds, Fortress security became a matter herding them away from construction sites with dog sentries moved around pastures pushing them away from the Fort.
Overconfidence led me to make the first attack order. The Dwarves chased the badgers with the dogs in tow, until the giant badgers stopped running away from them, and instead turned back to attack. There were heavy casualties almost immediately, with the majority of the hunting party and the dogs wiped out. One giant badger made it away.
The military had been humbled and learned its lesson. It grew larger, the dog packs growing in size and just in time to hold the ever more numerous giant badgers at bay. I even began capturing them in cage traps for a new Colosseum, a beautiful work in progress. Several things were to go wrong, the random number gods had willed it. A soapmaker had released all the giant badgers in the Colosseum, leading to pandemonium and massive death amongst the civilians. Discontent was rising, fights beginning to break out. The military were holding everything together when the goblins attacked. There were no more than a dozen of them, against many more their number of Dwarves.
Outnumbered and meeting the Dwarves on their homeland, the goblins destroyed the Dwarven military. I still remember seeing all those Dwarves break against the goblin line, metal spears and swords giving no mercy to the warriors before them. I had just learned the terror of metal weapons and metal armour. The dogs fought to the last after their Dwarven comrades had died. In panic I tried to use the time they had bought to seal off the aboveground workshops that had tunnels leading into the underground, but to no avail. It is possible that the reserve forces I had gathered might have been able to take on the invaders, but it was not to be so. After weeks of brutal fighting against the goblins, the gods further cursed our Fort by making the river freeze. All the giant badgers from beyond the river now had free reign to cross over, and there were no dogs to stop them.
The last Dwarf alive was a miner, who I prayed was my Fort's salvation. He walled himself off with the food and alcohol supplies and began carving out a domain, hoping to stay alive long enough for relief to come from migrants. The goblins found a way in, and the Fort died.
Metal is not a thing to fuck with.