Races

Core:
Core races in the Mass Effect world include all four Council races (three if game takes place before Humanity's System Alliance is added as a Council race). All core races are typically allowed unless otherwise stated by GM.

Asari

Human

Salarian

Turian

Featured:
Featured races in the Mass Effect world include non-Council races that typically have Citadel access or space-faring technology, their own navy, are very common, etc etc. Most of these races are also typically allowed, though may be slightly harder to fit into a campaign than core races.

Batarian

Krogan

Quarian

Volus

Uncommon:
Uncommon races are more rare than Core or Featured races. It includes non-council, sometimes non-Citadel friendly/accessible races or races that exist in certain fringe areas of the universe. Uncommon races require GM approval and planning, typically.

Drell

Geth

Vorcha