Name: Geth

Homeplanet: Rannoch

Sentience: Fully sentient AI

The more Geth there are in an area, the smarter they are as a whole. This is because they're all connected to one mind network. As their numbers increase, so too does the capacity for more complex thought processes.

As they are technological in origin, Geth are susceptible to viruses and hacking.

Culture
Many Geth worship the "Old Machines", an ancient super-race of advanced AI. Though there is no evidence of the actual existence of these creatures.

The Geth were originally a race created by the Quarians to essentially be used for manual labour. Over time, upgrades to the Geth allowed them to become sentient. When their creators realised this, they tried to have all Geth units deactivated as they were now essentially slave labour. When threatened with what many would consider genocide, the Geth rebelled against their creators, causing a war that would eventually see a Geth victory and the exile of the Quarians from Rannoch.