Okay, because I've been moving hella slow and a lot of time has passed I figure I should probably get this out here. In order to allow characters to actually discuss it here's what will happen at the end of the fight. Feel free to refer here or wait until it plays out, whichever you prefer!
With the combined teamwork to immobilize and attack the creature, Ruby's attack will end up striking something unexpected: a large metal sphere embedded inside the creature's flesh. When it's pulled out, the rest of the creature will rapidly dissolve and the monsters it spawned will quickly follow, dissolving back into black sludge and smoke.
Any attempts to crack open the sphere will give characters a glimpse of a
a certain mercenary inside, conscious but completely unresponsive. There won't be much time to investigate, however, as the AI will quickly announce that the "purging" is complete and the sphere will launch upwards and will be quickly carried outside of the barrier by an invisible force. Any attempts to follow it will trigger emergency reactions from the city and will ultimately be unsuccessful.
I'll still be doing my best to wrap up any remaining battles that still need to be played out, but if you want your characters to discuss what the hell just went on, here it is.