Released in 1990, the Mega Core Magnetizer (set 6989) was the keystone kit in the first run of M:Tron, the series that marked the beginning of the end for the classic space line. Already dabbling with themed sets after the success of the Blacktron line, Lego began several themes in the Mega Core Magnetizer that continued throughout the '90s, like larger and more gimmicky pieces. To Lego's credit, many of those new pieces continues to be used in sets to this day—the new magnet pieces and large wheels are used in the Star Wars Star Destroyer model, for instance. But while the large wheels and windscreen allowed the Mega Core Magnetizer to appear to be more substantial than previous kits such as the Blacktron Battrax, they also heralded the large, single-use pieces that would haunt Lego sets for the next decade.

Nevertheless, the Mega Core Magnetizer offered a still-appealing design, with multiple mini-fig vehicles and a working magnet-clip crane. Plus, the florescent cone blocks that shipped with M:Tron sets graced the fronts of homebrew space ships and laser rifles for years to come.