It’s an Olog-Hai.
Leandro over at the Spanish site Elfenomeno sent us a bit of news about one of those ‘Troll’ pictures we saw recently. He’d heard from the super-spy Galadriel that this thing is an Olog-Hai, or a hill-troll. They’re described at the end of Appendix F1, ‘The languages and peoples of the Third Age,’ where it says that they were bred by Sauron.This is what falls on Pippin, at the end of the chapter ‘The Black Gate Opens.’
The picture of this CGI beast is here, scroll down to the news for June 20th.