Just gonna throw this out here. I really do think that Agatha Harkness is being controlled by someone, probably Mephisto or Nightmare and the "engineer" is still not revealed. Agatha first appeared on comics in Fantastic 4 as Franklin Richards nanny/caretaker and she's not really a "good" character but she was not innately evil. I think Disney is pulling that card of subverting expectations about the engineer in episode 7 so when they finally reveal who he is the fan reaction will be humongous. I still trying to hold on to hope that Reed Richards will appear haha. That said I won't be betting on it. Agatha is almost a blank slate of a character that they can pull from the comics. She worked mostly as a side character and a plot device. I just can't stop thinking that Disney would make sure a huge deal in hyping this engineer, the person that gave Monica the truck wasn't the engineer and they made sure to indicate that and the connection that Agatha was introduced in F4.

TLDR Agatha first appeared in F4, Reed Richards still possible.