Despite what you might have heard, the first golem was created not by a powerful mage or an elven Sage, but by a simple dwarf from Maribor named Bonaventura Sesto - a brickmaker.
The fateful act of creation took place over a century ago, when the persecution of nonhumans was in full swing in Maribor. Elves and dwarves had been accused of bringing an epidemic to the city - though it was later discovered the outbreak had been caused by a man named Mattheo, a barkeep's dogsbody at the Golden Goose Inn. This Mattheo was charged with both serving meals and cleaning the latrines, and would only wash his hands once a month, and then not very thoroughly. The rest, as they say, is history.
The persecution of nonhumans was limited at first to robbing their shops, arson and the occasional beating, but the violence soon escalated into a bloody pogrom. As the city guard looked on without lifting a finger, humans murdered elves and dwarves during three days and three nights of slaughter, killing over three hundred individuals, including the aforementioned Bonaventura Sesto's entire family.
Driven mad with grief and thirsting for vengeance, Bonaventura molded a ten-foot-tall humanoid out of clay, and then carved the names of the slain nonhumans onto it, along with a smattering of dwarven curses. Once finished, he slit his own throat - and when his blood splattered the gigantic statue, it came alive and started walking towards the city. Bonaventura had his sweet revenge on his persecutors - his creation killed almost five hundred humans, including the mayor and the entire city council, before the soldiers of the city garrison could take it out using their ballista.
The Conclave's later investigation found that Bonaventura had possessed hidden magic talent. Though he had never had any training, the torrent of powerful emotions running through him at the time of his death flushed out his latent powers and created from them a new spell. After numerous alterations and improvements, one can now cast this spell without sacrificing one's life - and golems guard laboratories, libraries and palaces across the Continent.