Promethean Crawler

The Crawler is an autonomous Forerunner defense construct, designed by the Promethean Warrior-Servants as a means of asymmetrically combating the Flood.

Overview
Crawlers are small, quadrupedal machines capable of both ranged and close-quarters combat, using a built-in Boltshot as their primary weapon; this weapon disintegrates targets to prevent their biomass from being co-opted by the Flood. Unlike the majority of Forerunner automatons, they lack anti-gravity capabilities of any kind and instead rely on their four legs for locomotion. Crawlers are ferociously aggressive, having been specifically designed to hunt down and eliminate any foreign threats, their inorganic nature making them immune to Flood infection. They travel in large packs and work together to destroy enemies by overwhelming them from every conceivable angle, relying on skirmishing tactics.

Crawlers are often directed by Promethean Knights, who regard them as cannon fodder. They are protected by Watcher Sentinels, which can offer them cover in the form of small hardlight shields or create new Crawlers from raw materials in the ground. In addition to the basic type of Crawler, a more heavily armed unit and a long-range unit are also employed.

At the start of the UNSC's first engagement with Promethean forces, Cortana noted that the Crawlers' AI is similar in structure to that of the Promethean Knights; this suggests that they may also be created from humans processed by the Composer.

Numerous Crawlers were encountered by UNSC Defense Force and Covenant personnel on the shield world Requiem in summer 2557.

Subtypes

 * Crawler Snipe - a further upgraded long-range Crawler variant with a built-in Binary Rifle.
 * Alpha Crawler - a variant which leads packs of lesser Crawlers and utilizes a Suppressor in combat.

List of appearances

 * Halo 4