When Guillermo Del Toro's plans for a film adaptation of H.P. Lovecraft's novel At the Mountains of Madness were shelved more than 2 years ago, it was mainly due to two reasons. On the one hand, its content shared many similarities with Ridley Scott's Prometheus since the Lovecraft story also revolves around extraterrestrial beings that gave the impulse for intelligent life many ages ago.

Del Toro: "Same premise. Scenes that would be almost identical. Both movies seem to share identical set pieces"

On the other hand, the rating situation played an important role. Del Toro considered it an absolute necessity that the film was made on a level that would require an "R" rating. The dark horror story should not have to be compromised by squeezing it into the boundaries of a "PG-13". But the problem is that the film would probably be very expensive with a budget of up to $200 million being discussed. The risk for a film aiming at a mature audience is thus quite high. It's rare that films with such costs and an "R" rating turn out to be profitable for the studios.

Interestingly, the film is now a topic of discussion again. In a recent interview, Del Toro implied that he wouldn't have a problem with a PG-13 any more. The rating allows much more than some years ago. He doesn't mention the similarity problems with Prometheus which probably means that they aren't a problem by now, either.

Currently, At the Mountains of Madness is being discussed with the production studio Legendary. Del Toro would most likely film one or two of the very violent scenes in a manner that fit into the PG-13 boundaries. He explicitly mentions a scene in which the aliens perform an autopsy on a human.

Del Toro: That’s exactly what I discussed with them. I said to them, that’s the movie that I would really love to do one day, and it’s still expensive, it’s still … I think that now, with the way I’ve seen PG-13 become more and more flexible, I think I could do it PG-13 now, so I’m going to explore it with [Legendary], to be as horrifying as I can, but to not be quite as graphic. There’s basically one or two scenes in the book that people don’t remember that are pretty graphic. Namely, for example, the human autopsy that the aliens do, which is a very shocking moment. But I think I can find ways of doing it.

Shortly after he said that, he shared another idea with Collider:

Del Toro: So what I would like to do is shoot it, as dark as it is, in an unrated cut and a PG-13 cut. Ideally they would be released simultaneously if that’s at all possible. We could release one [cut] in a certain format and the other in a different format with the hopes that we can offer more intense moments in one cut and equally intense moments but without graphic content in the other cut.

However, it's unclear whether he imagines the Unrated Cut as something that could come with the home video releases (which is a perfectly common strategy) or whether he would really want to release both the PG-13 and Unrated in cinemas simultaneously. At least the latter plan would face strict MPAA regulations that e.g. prompted the makers of Anchorman 2 to wait for quite a while before releasing their alternate version theatrically for a week. Getting two versions of the same movie with different ratings into theaters doesn't fly with the rules. Theoretically, though, the Unrated Cut could be shown in IMAX cinemas alone while normal theaters would get the PG-13. Maybe that's what Del Toro means when he refers to "certain format".

At this point, nothing is really confirmed but it certainly looks brighter than it did in a long time. Maybe it could happen after Pacific Rim 2.