Promethean Crawler

Promethean Crawlers are an unit of advanced form of artificial intelligence created by the ancient Forerunner race alongside other models of Promethean including Knights and Watchers that appear in the Halo Universe.

Physical Appearance
Crawlers have a very distinct appearance, seeming to look vary similar to various species of small, four legged animals. They have a very strong armor platting, similar to the Crawler's fellow Prometheans, but seem to lack heavy armor on their head, as they can be easily destroyed when shot in the head. Early units of Crawlers, as seen on the Forerunner created planet of Requiem, where silver in color, but later variants of the standard Crawler, like the ones used in Cortana's Created, were more a dark grey and almost black color.

History
Promethean Crawlers have been used by the Forerunner race for years, being created during the final years of the Forerunner-Flood War and being placed on key Forerunner worlds to aid in the fight against the Flood infection. The most notable use of Promethean Crawlers being when the Forerunner known as The Liberian placed several Crawlers, along with other Prometheans, on the artificial planet, Requiem, to guard the rogue and insane Forerunner, the Ur-Didact. These Crawlers would later be encountered by the human soldier, Master Chief, who ended up accidentally releasing the Ur-Didect from his prison and used his powers to take control of all the Prometheans on Requiem, including all of the Crawlers. Later, after the Ur-Didact's death at the hands of Master Chief and his human-created A.I., Cortana, all of the Crawlers under the Didects control were put into use in the Sangheili, Jul 'Mdama's Covenant remnant for a brief period of time until they came under the control of Cortana and her Created, rebelling against the Covenant to join the Created.

Alpha Crawlers
Promethean Alpha Crawlers, also known as Prime Crawlers, are an variant of Promethean Crawler that are designed to act as the leader of a designated group of Crawlers. They can be easily identified by the spikes on their back and unique head design. Alpha Crawlers are usually seen in smaller amounts than standard Crawlers. Similar to standard Crawlers, most Alpha Crawlers were silver in color, but later units where seen with a white tint instead. It is possible that this color change from silver to white may be to better tell the Alpha Crawlers from the standard Crawlers and Snipers.

Sniper Crawlers
Promethean Sniper Crawlers, or Sharpshooter Crawlers, are an variant of Promethean Crawler that, as their name suggests, are equipped with a Z-750 Special Application Sniper Rifle and are programmed to attack threats from a distance.

Appearances

 * Halo 4 (first appearance)
 * Halo: Spartan Strike
 * Halo 5: Guardians