If a TPK happens because the overlord attacked with lieutenants, what happens to the party's action that week? I'm assuming nothing changes, since an action that hasn't started yet can't end, and because the overlord being able to negate the party's turn before it starts is a quick road to lock down. Is there an official ruling on this?

James McMurray said:

You answered your own question.
An action that hasn't started yet cannot prematurely end.

This is the sort of thing that there will never be an official answer for, and never should be an official answer for!

Thanks, that's what I figured but it's good to have confirmation.