Galleon fleets keep watch over Grineer mining operations that penetrate Mercury's asteroid field. Cavernous rooms and twisting metal corridors mark where labourers have stripped the region for natural resources, transforming the natural landscape to support Grineer occupancy.
Grineer are all clones from a genetic pool of 'Originals'. They are able to extend their lifespans with recycled cloned parts, but their genetic material has degraded over time, and haphazard repairs have made many of them look oddly deformed and susceptible to skin diseases. Through decades of service, many of the Grineer elite can cover the expense to have flawed organic parts replaced with cybernetic augmentations.
The Old War found humanity facing a technologically superior force, and their own weapons were turned against them. Melee and ballistic weapons, inspired by primitive counterparts, became part of the Tenno arsenal to circumvent the Sentient interference of more technologically involved weaponry.