Arche

Arche is a microscopic nanomachine that has contaminated much of planet Earth by the present time of Black★★Rock Shooter DAWN FALL.

History
Arche was likely meant to be used for Project Elysion. However, because the project's core artificial intelligence, Artemis, chose to attack humanity and went on a rampage, the nanomachine went out of control and contaminated the sea before being spread into the earth. By the present time, the planet's ecosystem had rapidly changed because of Arche, which had even polluted the air to the point that normal humans require a respirator at all times outside. The Arche in the sea gave rise to the Iron Ocean, where captured humans are thrown into to draw out the energy of the machines.

Arche are what the weapons wielded by Empress and Strength, the Coilgun and Gigantic Arm respectively, are composed of. In the case of the Coilgun, it requires a certain amount of Arche to be fully formed and used.

Etymology
Arche is derived from the Ancient Greek word ἀρχή (arkhḗ), which means "beginning" or "origin". In ancient Greek philosophy, Arche is the first principle, or underlying substance, of existing things.