Arch Guardians are guardian enemies in Borderlands. In the original game, Arch Guardians only appear in the Eridian Promontory (not including the few Arch Guardians that appear in Reactivate the ECHO Comm System). They may also randomly spawn during advanced matches in the Mad Moxxi's Underdome Riot DLC.
They have thin bodies that curve around, very thin arms, long thin necks and a very small head. They also bear a twin set of curvilinear cannons on their backs, a feature unique among Guardians. They are some of the most alien-looking creatures on Pandora, and along with their large size and unique shape, they are easily identified by a distinct bone white color, with detailing in bright blues and violets.
The Arch Guardian has two main attacks. One is a very long-ranged attack utilizing the twin plasma mortars on its back. These fire volleys of multiple large, oscillating charges of energy, with an arcing trajectory and impact splash damage common to most forms of artillery. The shock damage from this attack can decimate the shields of any targets caught within the impact radius.
The second attack is used on targets at close range where Arch Guardians swing their arms in alternating fashion. From their right hand they launch a fast moving direct-fire energy bolt. This attack is difficult to avoid due to its sheer speed, but its damage output is considerably weaker than that of the plasma mortars. From their left hand they launch a small energy blast which distorts the victims' view. If the Vault Hunters get into melee range, Arch Guardians will deploy energy blades and slash their victims.
There are two main tactical approaches that are effective against Arch Guardians. The first is to maintain distance and try to score critical hits on the faceplate with a sniper rifle. This usually involves evading the powerful artillery shots of the Arch Guardian and staying close to cover, or merely staying out of its attack range. The second strategy is to close the gap, pressing the Arch Guardian to switch to its weaker close-range attack. By strafing the Arch Guardian, many of the direct-fire bolts can be avoided, although other Guardians in the area can pose a considerable threat, so this tactic best employed after they have been eliminated or if the Arch Guardian is alone.
As with other guardians, shock damage inflicted on them can deplete their shields easily. They have moderate health and aren't particularly mobile, making most weapons effective at delivering the fatal blow.
The Hunter's Trespass skill makes him most effective at incapacitating these foes from the longest range possible. The Soldier is well advised to drop his Scorpio Turret in range of an Arch Guardian and then separate from the turret to split the Arch Guardian's offensive power.