Legion

A legion is a generic term for a type of military unit. The term was originally used to describe an infantry unit in Ancient Rome; the general size of these units fluctuated during the military history of the Roman Empire between approximately 4,500 and 5,200 soldiers, the equivalent of large regiments or brigades in the UNSC Army and Marine Corps.

Covenant
In the Covenant military, a legion was a large administrative grouping of Sangheili warriors, commanded by a high-ranking officer. Legions were expected to operate as a combined-arms force. While typically non-permanent formations, warhosts that proved their skill in battle were occasionally adopted by legions. The Dn'end Legion was a respected legion of the Covenant.

Warrior crèche
A "warrior crèche" is a type of legion where newer warriors hone their combat skills before being assigned to a regular legion. Warrior crèches seem to be specifically used for ground combat, and are carried aboard Covenant fleets should any ground actions be needed.

Warrior crèches

 * N'Nono Warrior Crèche
 * E'Toro Warrior Crèche
 * R'Lan Warrior Crèche

Forerunner
In translated Forerunner records, the term legion is used in reference to a type of Warrior-Servant organizational unit.

List of appearances

 * Halo: Ghosts of Onyx
 * Halo: Cryptum
 * Halo: Silentium
 * Halo: Broken Circle
 * Halo: Ground Command