He steps outside, and is introduced to nothing but thick jungle. No signs of life, maybe a bug here and there. He wanders through the jungle and this will be the first third of the level, using branches for platforming purposes. Halfway through the jungle, he encounters a thin river. He follows the way it flows out of the jungle. He comes across something like this
http://i.kinja-img.com/gawker-media/image/upload/s--reaM3qrh--/18lp2sugl4u7ajpg.jpg, the ruins of an old civilization.
He explores the area and finds that whatever ended these people did so violently. Blood on walls, crumbled stone buildings etc.
He reaches the top of the hill and finds another temple. Inside are hints of ritual sacrifice. Other altars with either skeletons on top, or better yet, a pile of ash so it looks like they were burned. Around the altars are white circular designs (we will find out in later levels that the circles are meant for holy protection. So right now the player doesn’t know why these people were sacrificed).
He keeps wandering through the temple and hears some rattling. Behind a door and locked in a rudimentary cage is a zombie, halfway decomposed, scuffling around on the floor. It sees the PC and struggles toward him but is harmless behind the bars. More decomposed zombies lie in the cage but they are hardly recognizable, just darkened slabs of meat. If and when the PC enters, maybe include a HUD disorientation of an animation of him reacting to the smell.
He leaves and comes across another artifact. Taking it, he teleports further on.