Millium is an artificially created human, a homunculus, that was created in the Black Workshop along with her sister Altina Orion. She was adjusted to link with Airgetlam, a combat shell. Millium gained consciousness in S.1199 when she woke up in the care of Giliath Osborne, Lechter Arundel and Claire Rieveldt. She then joined the group known as the Ironbloods.
As a member of the Intelligence Division, Millium is introduced after invading the Aurochs Fort east of Bareahard, Erebonia.