Promethean Crawler

"These are Crawlers—fast and mean, but pretty easy to deal with."

- Jared Miller describing Crawlers to Fireteam Crimson

The Crawler is an autonomous Forerunner defense construct, serving as part of the Ur-Didact's mechanical Promethean army 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 Z-110 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. They are however capable of vertically scaling structures and leaping great heights in order to get tactical advantage. 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.

It is unknown for what purpose the Ur-Didact originally used Crawlers for. It has been theorized they were sent into Flood strongholds to soften their infantry numbers before more valuable assets were sent in. Numerous Crawlers were encountered by UNSC and Covenant personnel on the shield world Requiem in mid-2557 during the First Battle of Requiem, and later during the Requiem campaign in February 2558. Crawlers also accompanied the Didact during his attack on the human forces on Installation 03 and at the Composer's Forge.

Behavior
Crawlers in Halo 5: Guardians exhibit animal-like behaviors throughout the campaign. They can be found "sleeping" outside of combat, scratch themselves with a back leg similar to wolves or dogs, and will even show distress (i.e. by whining, as Exuberant Witness explains) if kept isolated from other crawlers. Why these behaviors would be (presumably) programmed into units that are used as canon fodder is unknown.

Subtypes

 * Crawler Snipe - a further upgraded long-range Crawler variant with a built-in Z-750 binary rifle.
 * Alpha Crawler - a variant which leads packs of lesser Crawlers and utilizes a Z-130 Suppressor in combat.

Trivia

 * Promethean units were named for chess game pieces during Halo 4's development. The Crawler was originally called the Pawn. It remains the character model's file name in the game code. Only the Knight retains its chess piece name.
 * The Crawler, along with the Promethean Watcher, was first seen in a leaked image from McFarlane Toys.
 * In the Spartan Ops mission Switchback, a Crawler can be found wielding a lightrifle, which it holds in its front right foot as opposed to in its body like other Crawler units.

List of appearances

 * Halo 4
 * Spartan Ops
 * Halo: Escalation
 * Halo: Spartan Strike
 * Halo 5: Guardians