The Grid are mechanical constructs in Defiance.
The Grid are capable of taking over other races such as Humans, Irathients, Sensoth, Liberata and Ninety-Niners; when the body of these hosts are destroyed, the Grid can manifest itself. The EGO devices used by Dark Matter and the Bay Area Expedition Ark Hunters are resistant to Grid influence and their influence can be purged from others. The Pilgrims of the Guiding Light revere the Grid and view their actions as "righteous work".
The Grid were originally Modunauts; automated machines that maintained the Arks on their journey to Earth. They began showing up in the Bay Area in 2047 from Silicon Valley and first appeared in San Francisco, attacking Dark Matter at Downtown. They attacked and infected Charlie but their influence was purged by the Pilgrims as he was not ready for it. They later infiltrated Presidio Bunker where they attacked the Echelon Mercenaries that had been hired by Melak Vor and took control of several of them, before finally affecting Melak himself. Some Grid joined the Pilgrims aboard an Ark that was planned to be taken to the Alpha Centauri system.