Nope. There is ALWAYS a regroup phase except at Site 9 (when the Ring-bearer merely has to survive until the end of all skirmishes).
Unless you're playing Tower block and someone slaps down Caverns of Isengard as their site 9, but good luck running into that situation.
That actually has happened in a card game between Gog, me and another, that will hopefully join this site as Urkenbran95. It comes to the last site and of course, Gog is ahead of me and the other person, so he's like "yay, i win" and "it's your site, hurry up" so i just slap down the caverns and he is totally P.O'ed. Thus he comes at me and just when he's a few feet off of his attack on me the full moon appears through the window, suddenly we hear a tear, rip, and then a growl, and the beast is upon me fur bristling jaws snarling and snapping-Jk lol.