Your party (an adventurer, your army, or otherwise) discovers a large pile of cogs and metal things far from your main city.
You send an engineer to look it over. He/She determines it is an old ruin! Ruin’s have many secrets to study, but also indicate that something horrible happened there (and may happen again). You can set your engineer to study the ruins secrets, but it will take time (two in game hours).
Because of the time frame, it is best to build a small home near the site and defend it while the engineer works. In that time, monsters attack sporadically.
Once the engineer is done, he explains the ruins belonged to an ancient race with advanced machinery. He believes he has found schematics to re-create one of their great helpers!
Once crafted (which includes a bit of magic), it turns out to be a clunky steam robot! It moves slowly, but is immortal (to a certain extent) and has stat boosts to creating weapons! Your engineer also gains experience.