User blog comment:IamJakuhoRaikoben/Chapter 375: Supernatural, Review./@comment-3424593-20140314111920/@comment-24066070-20140314131315

We don't know how Face is activated, but it may have a control panel (which Ezel destroys) or a password or some other way which makes de-activating it impossible for Wendy.

If that's the case, Wendy or anyone else coming to deactivate it would be unable to do so and Ezel can just rush back on his many legs in order to help Tartarus fend off FT.

So I think it's rather good he stayed behind to make absolutely sure nobody will de-activate it.

Then again, since we don't know anything about it, there may be a simple off-button, but that would be very simple-minded. After all, it's a super-weapon and not a simple lightswitch.