During the Mirage War, Zhalfirin sailors discovered, on the north-western coast of their country, a barnacle-encrusted chest. Inside of it, they found a scroll of circle of protection, the remains of an artifact, and a journal containin the story of the Zhalfirini ship Wavecrester and of the Steel Island.
Two years before, the Wavecrester traveled to the Burning Isles in order to make the waters clean from renegades and pirates. After succesfully scouring the seas from pirates, the ship reached a mysterious island. As recorded by the crew of the Zhalfirin ship, the island was barren of life and dominated by a gigantic castle. A whirling aether-storm surrounded the castle's tallest spire. Inside were emotionless, mechanical clockwork gnomes busy building legions of flying servants. All of the creatures, gnomes, clockwork avians and mechanical wasps alike, were constructing a massive dreadnought of metal and sorcery, a destructive artifact the likes of which pre-Invasion Dominaria had never seen.
The journal calls the isle "Steel Island" and gives sketchy details of its history. It was thought that the unnaturally intelligent gnomes sought only to fulfill their orders and return to their creator by building the biggest artifact to ever walk on the plane. Then they planned to enchant it with flying so they could search for their master.
A confrontation between the Wavecrester and the gnomes ended with the reported demise of the former and the flight on their dreadnought of the latter.