There are two stories in Legion of Super-Heroes 19 (Feb 86), both by Levitz.
La Rocque and Mahlstedt provide the art on the lead story, which is a follow up to the Sun-Eater factory tale. Readers wrote in wondering more about the situation, and that probably prompted this follow up, which begins as Ultra Boy, Phantom Girl, Element Lad, Shrinking Violet and Chameleon Boy get dramatically warped away from the rest of the Legion.
The team gathers to wonder what has happened to the missing members, who they quickly notice are the same ones who went missing before. This time the Legion is not left in the dark, the Controller who kidnapped the five shows up in the Legion's headquarters to explain that he is behind their disappearance.
We, and the five Legionnaires, learn that the Controller had been constructing the Sun-Eater in order to use it as a weapon to destroy an artificial world constructed by Tyr. Honestly, it looks a bit more like a giant space ship than a planet, but who cares. It's big and deadly, and beyond the powers of the Legionnaires to stop.
Dawnstar, Mon-El and Wildfire set out to try to find their missing comrades, but Brainiac 5 is still obsessing over the identity of Sensor Girl. In pretty much every scene that she is in Sensor Girl displays an awareness of things she could not possibly know, and Brainiac 5 even thinks she is able to sense that he is watching her on the monitors.
Chuck Patton and Mike DeCarlo do the art on the back-up story, which centres on Invisible Kid. He has been working with Dr Gym'll to gain a further understanding of his new powers. I ought to mention that Invisible Kid has been cleared of responsibility for the death of the Khund, it being determined to have been in self defense.
Dr Gym'll informs Invisible Kid that he is able to remove the new powers, should Jacques want that. Dawnstar and Wildfire play small roles in this story as well, and the three stop an attack on Medicus One. At the end of the tale, Invisible Kid opts to have his new powers taken away, and remain with just the one he is able to fully control.