Lore

Updated: 8 October 2026

Milkhama Island: Arashi, Steel Troopers (ST), and the timeline of events before and during the story.

Milkhama Island

Milkhama is a volcanic island that rose from the ocean where an asteroid fell. Its deserts hide Arashi, an ore found nowhere else. Arashi turned simple bipedal work machines into Steel Troopers (ST), the mechs you command, and made the island the prize of two superpowers and a dozen corporations. The in-game calendar counts years as XC (the New Era); the story begins in XC 116.

Term	Meaning
Arashi / Arashium	The island's unique ore. Freed from its sulfide shell it becomes a glossy liquid metal that changes its properties under extreme physical conditions; the alloy made from it, Arashium, is in every ST. On the exchange, Arashi costs more than gold.
Steel Labor → Steel Trooper	Steel Labor is Obsidian's Arashium-enhanced bipedal engineering machine. Its military version, the Steel Trooper (ST), takes swappable weapons and is built from three part types: body, arms and legs.
Nerve Aurum	An alloy made from Arashium; its magnetic variance allows two different lines of development.
Augmentation (Hyper-Aptamer)	Surgery that wires a pilot's nerves straight into the ST's biosensors for control no normal pilot can match. Its surviving test subjects formed the rebel group Epiphyllum.

Timeline

When	What happened
91 years before the New Era	An asteroid falls into the ocean. When the undersea volcanoes calm down, an island of volcanic ash, Milkhama, stands at the impact site.
31 years before the New Era	The Dawnstar League (DL) is founded.
XC 75	Obsidian finds Arashi deep in the central desert mines. A gold rush follows: an Arashi exchange opens, nations and corporations pour onto the island, workers go down the mines.
After XC 75	Obsidian releases Steel Labor; its military version becomes the Steel Trooper. Mine collapses and Arashi poisoning hit the workers while promised protections never come, and the unrest grows.
XC 82	The DL lands on the island; today it governs East Milkhama.
Until XC 101	The Milkhama War. The DL loses to the coalition; afterwards the two powers split the island between them.
XC 116	The story begins: Kaidan's squad answers a UNCS distress call in the Parill Desert. See Story.