The casualty is Johnny Storm, brother of Sue and best buddy/antagonist of The Thing. Also one time JO Buddy of Reed, but it was just that one night and they both had a lot to drink and maybe Dr. Doom had hit them with a ray or something.
Oh well! It’s not particularly interesting. I’m sure Sue will be a mess and Ben will go off and be morose again, but I find it hard to care - and that’s not even knowing that while Fantastic Four is being ‘canceled’ and a new book is taking over the series hits issue 600 in just over a year, and it’s likely that they’ll bring back Johnny by then and resume the old numbering.
You gotta do better, comics.