From Lexicanum

The Ring of Iron was a chain of construction yards that surrounded the Adeptus Mechanicus world of Mars.

The original exploration vessels were constructed in these orbital factories with the Expedition fleets of the Imperium of Man being built in them. During the Martian civil war at the start of the Horus Heresy, the Ring of Iron was attacked and devastated in the conflict with fire on it being seen from the red sands on Mars.¹

Source

• ¹:Mechanicum (Novel) by Graham McNeill

This article is a stub