The Rock Lords were a line of transformable rocks marketed by Tonka in conjunction with their ongoing GoBots series. Based on similar transforming rocks in a subline of Bandai's Japanese Machine Robo toyline, the action figures featured bio cards highlighting their strengths with reference to the type of stone they were said to represent. As an attempt to edge in on the booming transforming robot market being dominated by Hasbro’s Generation 1 Transformers, the Rock Lords’ entry in 1986 proved to be too little, too late to help the GoBots compete.
Each Rock Lord came on a blister card with a stony-textured weapon, and could transform into a "rock" of a type specified on the stats card. They also included a mini-comic, illustrating one of their battles. The figures were often textured to resemble a type of stone, sometimes illustrating fractures or lumpy mineral structures. Almost all were cast in multi-colored swirled plastics, except those that were coated entirely in vacuum-metalized "chrome" to represent metal ores. Later additions to the line were Rockasaurs, larger dinosaurian beasts that transformed into boulders, as well as Narlies, the furry non-transforming fauna of planet Quartex. Rock Lords eventually expanded beyond its Machine Robo roots by introducing the Action Shock Rocks, who eschewed a weapon accessory in exchange for a spring-loaded or motorized action feature.
The Rock Lords toyline was supported by a cartoon movie animated by Hanna-Barbera, and featuring stars like Telly Salvalas voicing main characters. The movie made clear the Rock Lords' tie to the GoBots, but failed to impress, and the line barely lasted beyond the year of its introduction. Due to the obscurity of the later additions to the line, it is uncertain how many figures were released in 1987, if any.
The Rock Lords were also sold in Europe ostensibly as part of the Robo Machine: GoBots line, and as part of Australia's Machine Men. For unknown reasons, the first wave of figures were released in Europe with altered weapon colors, and the final wave of Action Shock Rocks were also recolored in non-US markets. The combiner gift set Fossil Saurus was intended for mass release, and featured in the movie, however, he was scrapped from US markets, only to see release in the Revenge of Cronos portion of Machine Robo as BH-04 Gattai Saurer.
As GoBots faded to obscurity and died by 1987, Rock Lords died with it. Despite its much-maligned theme choice, the more common Rock Lords toys are somewhat ubiquitous in the second-hand market. True to their name, a stone-like durability leaves even the most heavily-worn samples unbroken decades later.