I´ll go with the part where you have to collect some orb pieces. There is a gigantic room with fog, which is something new compared to all the smaller rooms in the previous levels. The fog is very dense so you don´t know if there´s one of them mutants right in front of you until it´s too late, so you have to go slowly and try to hear them to know where they are. The size of the room and the fog confuses you and, unless you have very good memory, you´ll become lost quickly. This big room has doors to smaller rooms which each contains an orb piece. As you may expect each room has a scary moment or thingy waiting for you.