Auxiliaries are troops that act in support of the army they serve.
During the Great Crusade, several units of the Imperial Army were raised from, or trained on, the homeworlds of the Space Marine Legions, and accompanied their "parent" legions on their Expeditionary Fleets, naturally adopting many of the same traditions, organization, and livery.
|Castellax Janissaries||Iron Warriors||Castellax|
|Castellax Mamelukes||Iron Warriors||Castellax|
|Selucid Thorakite||Iron Warriors||Olympia|
|Prospero Spireguard||Thousand Sons||Prospero|
|Ultramar Defence Auxilia||Ultramarines||Ultramar|