This is a surprisingly good horror movie, along the lines of THE RUINS and THE DESCENT. A new pyramid is discovered from a much older Egyptian Dynasty. The weird thing is that it has only three, not four, sides. At first the archeological team sends in a robot, equipped with cameras, to explore, but it's damaged so they have to go in and retrieve the million-dollar device. What they discover, after they become trapped within, is that they are not alone. There are these strange yet familiar animals that are preying on them. And there's also something much larger, which is why the huge pyramid was buried beneath the ground.
This is a one of the best horror films released in 2015. If you're a fan of such movies as THE CAVE or THE DESCENT, you'll dig this one.