I'd suggest reading through some previous ones for a good idea of how they work.
“Mission control, I’m entering the building now.” As a lonely hero approached a depilated warehouse, they found their transmission becoming overtaken by static. Shutting off the feed, they resigned themselves to carrying the mission out without backup. They were a veteran, having seen many a villain and many horrendous deeds done. They had stopped many more of those deeds, however, and while experience had sharpened their skills, it had yet to dull their optimistic belief in their duty to undo wrong. Still, as the wind moaned down the abandoned city streets, their robotic hands tightened around the grip of their cannon unconsciously. Something didn’t seem right.
Stepping into the warehouse, they found long aisles running between towering walls of stacked crates – their trained eyes could…
Twelve months prior
By the time more heroes had returned from their own successful missions, the imposters had disappeared, leaving naught but the shattered bodies of other heroes scattered about the factory. Zib was rebuilt, and restored to life with the backup of his memories – frustratingly but mercifully, that backup had been made before the incident had begun, and so he did not recall the event.
Long discussions among the Factory’s leadership were had, but finally it was decided that the public didn’t need to know what had happened. The storage room where the final encounter had taken place was marked off-limits to those without the proper clearance; the interior held only a small statue to honor the fallen heroes, who were marked as “Missing in Action” on official rosters.