All parts and accessories: TerrorTech (Remco ManTech, 1983)
Remco's ManTech toys were released in 1983. My brother and I each got one that Christmas, so despite the fact that they're just a cheap toy series, they've always held a soft spot in my nostalgic heart, in part because the villain designs are very cool. The paint apps were...minimal, to be charitable. So these customs are all just adding a great deal of painted detail to the figures to give them a little more life.
Early advertising indicated that a cartoon was in development, though that never cam to fruition. The only media support was a 4-issue comic series published by Archie Comics. A second series of toys was planned (including figures called EagleTech, KongTech, RobotTech, and SpiderTech) but never came to be.
In-universe, the ManTech warriors were created by Jaxon Goode (the good guys) and his rival Tyranik (the bad guys). The good guys were human astronauts whose mission went awry and ended up in suspended animation on the planet Mekka until Goode recovered them and gave them robotic bodies against their will. Fun!
While no biographical information is available on the evil robots, we have some background for the good guys. In the comics, TerrorTech is portrayed as being completely cold and logical, processing thoughts in the form of "Observation...conclusion."
Each figure was given a "Performance Profile", indicating what their abilities are. TerrorTech was rated for: Hi Therm, Sea Level, Sea Depth, Jet Thrust and Ion Trans (whatever that means).