Guardian (The Legend of Zelda: Breath of the Wild)

Guardians are powerful ancient robots able to shoot lasers from a small eye capable of rotating about, similar to a Beamos. They were created by the ancient Sheikah as a method to counter Calamity Ganon. While initially successful, were later taken control of by him, allowing him an easy way to lay waste to Hyrule, thus causing the Great Calamity. The primary Guardian type is the Guardian Stalker, recognizable by its tall cylindrical head and five legs. This type has many variations, and other types of Guardians also exist.

The Legend of Zelda: Breath of the Wild
In The Legend of Zelda: Breath of the Wild, Guardians can be found in various locations. Usually, they are alone or in small groups, but become increasingly concentrated close to Hyrule Castle. Remains of Guardians, mostly Guardian Stalkers, can also be found across Hyrule and can be used to salvage ancient materials from, though some, called Decayed Guardians, are still partially active. All active Guardians on the surface are controlled by Calamity Ganon and glow pink to represent the effects of his malice. In shrines, small Guardians known as Guardian Scouts appear to test Link, completely unaffected by malice. All Guardians are capable of firing explosive lasers, but they take several moments to charge.

As revealed in flashbacks, Guardians and the Divine Beasts were excavated in the time leading up to Calamity Ganon's return in hopes of using them to combat him as had been done a millenium prior. However, when he resurged he infected each with his malice, allowing him to lay waste to the land. Additionally, giant ancient stone pillars containing even more Guardians rose up around the castle, which the Hylians had been unsuccessful in locating. The Guardians began crushing all opposition, leading to a climactic battle at Fort Hateno where many were successfully destroyed with help from Princess Zelda's sealing power finally activating. However, the knight destined to seal the darkness, Link, was gravely injured and placed in the Shrine of Resurrection to spend a century being restored.

Hyrule Warriors: Age of Calamity
In Hyrule Warriors: Age of Calamity, more of the Guardian excavation is shown, along with their role in the Great Calamity. The latter, however, is altered due to a tiny Guardian who traveled back in time at the Great Calamity in order to prevent Hyrule's destruction. However, a trace of malice managed to travel back with it and possess its dormant past counterpart, creating Harbinger Ganon, intent on causing the Calamity regardless.

In-game, Guardian Stalkers, Guardian Skywatchers, and Guardian Turrets are all generically referred to as "Guardians" in their indentification titles, though the foremost again has its own subtypes. Unlike before, malice-affected Guardian Scouts also appear. The first enemy Guardian encountered is the primary enemy of the second stage, Road to the Ancient Lab, and is noticeably stronger than other normal Guardians in the game even when player strength increases from leveling up are considered. It is possessed by malice and pursues the player's team and must be weakened by having the small Guardian, Terrako, activate other dormant Guardians to fire lasers at it. Enemy Guardians are not encountered again until Calamity Strikes! and are found throughout the remainder of the game. Unlike the original game's timeline, however, the heroes manage to free the Divine Beasts with help from other travelers from the future, allowing them to lower the Guardian numbers enough to allow Link to get through the Battle of Fort Hateno unscathed and defeat Calamity Ganon.

In the Expansion Pass DLC, a Battle-Tested Guardian becomes a playable warrior. Unlike most others seen, it is unaffected by malice, and as such has orange lights instead of pink.

Trivia

 * While functionally more similar to Beamos, the actual initial inspiration for the Guardians was the original depiction of Octorok due to its sprite appearing fairly large relative to Link in the original The Legend of Zelda. Furthermore, their robotic nature was added to be more visually appealing than a large octopus.