In most G1 continuities, the Guardian Robots (GR) were powerful giant robots that kept the peace during the Golden Age of Cybertron.
Only one GR has survived into the modern ear, Omega Supreme who was the Guardian robot of the Crystal City.
Interestingly, we know little about these giants. The GR presented in the G1 cartoon that were not Omega Supreme were always blue and white and devoid of personality.
Takara recolored Omega Supreme into one of these GR as an e-HOBBY exclusive that used the same tooling as the Transformers Encore reissue of Omega featuring a retooled head. The Japanese name for the GR is “GADEP” which supposedly comes from the Japanese dub of the Generation 1 cartoon. Currently the only source for what the acronym means is the e-Hobby toy bio. e-Hobby says it means, “Groundling Auto-Destruct Powerbroker”
Omega Supreme was originally created from the original form “Super Change Robo Mechabot-1” produced by a company called Toybox. Toybox did not actually design Omega Supreme, instead commissioning his design, along with Sky Lynx, from Takara’s then-rival Tomy.
Consequently, Takara did not sell Omega Supreme in their original run of G1 toys so the toy was originally unavailable in Japan. When Takara and Tomy merged companies, Takara was finally able to release Omege Supreme and the blue GR under their Transformers franchise.
Transformers Animated featured Omega Supreme in its continuity. Guardian Robots were called Omega Sentinels in the Animatedverse, with Omega as the first created and last surviving member of his kind. Animated shrewdly used the original Robo Mechabots for inspiration in fleshing out their Omega Sentinel Corps.
The folks behind Animated used the black and red Mechabot as inspiration for the only known female GR – Kappa Supreme.
They also used the blue, red, and silver Mechabot as inspiration for Beta Supreme.
Takara’s e-Hobby GR recolor was used as inspiration for Ultra Magnus’ flagship Steelhaven better known as Sigma Supreme.
In the Animatedverse, Omega Supreme was the first of the Omega Sentinels, designed as part of Project Omega. The Sentinels were built to be living weapons to help turn the tide in the Great War.
Here are Beta Supreme and Kappa Supreme in my personal collection.
The Animatedverse isn’t the only continuity to refer to the GR as Omega Sentinels.
In the Dreamwave G1 continuity, we glimpsed the Omega Sentinels during the War Within storyline. Here, the Omega Sentinels were shown guarding various strategically vital locations in Iacon. During the Decepticon attack on Iacon, they were among the first and last lines of defense standing between the Decepticons and the Decagon.
The original mold used to make the Mechabots and the G1 Omegas is a great mold. I will mention that it is important to be careful with any of the original Toybox versions as they lack a retool implemented by Hasbro, and the lack of this retool makes the arms more likely to break off. This can be easily fixed by taking the chest plate off the original Mechabot figures and reinforcing the mold with putty or super glue. If you remove the chest plates on both the Hasbro mold and the Toybox mold, you can compare the two to see what I’m talking about.
Traditionally, Omega Supreme’s main nemesis is Devastator. In many continuities, the Constructicons were responsible for destroying Omega’s beloved Crystal City. No matter the continuity, the destruction of Crystal City is something Omega Supreme has never gotten over.
Of final note, I’d like to point out that not all GR come in a single size class. While many purists treat the Action Master Elite toy of Omega Spreem as an Omega Supreme variant, the Animatedverse made it a completely different (and much smaller) character.
According to the Allspark Almanac, Omega S.P.R.E.E.M. (Strike Prototype; Rapid Engagement & Elimination Module) is a small-scale prototype that preceded the Omega Sentinels.
The actual Omega Spreem toy was only released in Europe and Australia in 1991. He is one of the only Action Master figures that can actually transform, in this case into a tank. The original Omega Supreme figure was never released in Europe, and some use this (what they consider must have been Hasbro Europe’s ignorance about the original Omega Supreme) to explain the odd coloring and name spelling on this “variant.” However, I believe it is much more likely that Hasbro Europe intended for Omega Spreem to be an all together new character all along. After all, two of the other three Action Master Elites evoke, and possibly even homage, preexisting characters (Turbo Master resembles Bruticus and Double Punch resembles Black Zarak); yet, both of those figures are treated as individual characters separate from the previous figures that they resemble.
I personally really enjoy the characterization that Animated put forward that Omega Spreem is a smaller prototype of a GR. Until other characterization is given for this toy in some sort of official fiction, that is the explanation for Omega Spreem in my personal cannon.