GEOTHERMAL VALLEY - HOUSE OF THE AFFLICTED CHALLENGE TOMB
CHALLENGE TOMB ENTRANCE: To reach the first challenge tomb in this area, start at the broken wooden walkway that crosses the stream just north of the Remnant village. As you step onto the walkway, shoot the bull's-eye (5/8) hanging from the underside of the walkway a little ways downstream. Then follow the walkway as it continues eastward along the steep rock wall. When you reach the wide gap near the waterfall, shoot a rope arrow into the hanging rope coil and swing across. Just ahead on the left is an Explorer Satchel (1/5) that reveals the location of a number of survival caches and strongboxes, as well as several caves and both of the crypts in this level. (screenshots)
Crawl through the low opening into the little clearing beyond. Ready your weapon of choice and step forward to trigger the appearance of 3-4 wolves from the cave openings on the other side of the clearing. One or two poison arrows can be useful to start, but keep in mind that Lara can also take damage from the toxic gas. You'll probably need to switch to the pistol (or shotgun if you have it) to finish the fight. By all means, use the weapon you're most comfortable with in close quarters, since these wolves move in quickly and don't give up. When you've killed them all, collect their hides. Stand near the fence overlooking the water and look up on the left to spot another bull's-eye (6/8) hanging in a tree. Shoot it for the challenge. Then pry open the metal door and go inside. (screenshots)
Head up the stairs and follow the passageway into the ruins. There are several turns but no side passages, so you can't get lost. When you emerge from an arched tunnel of rough stone into a room with many clay vases and a few skulls, there's a stack of coins on the floor to the right. Take them and squeeze through the narrow gap in the wall ahead. Proceed through a dark, rocky tunnel into a flooded room with two flights of stairs with a huge metal cauldron in the corner between them. There's a survival cache (2/20) buried just to the right of the cauldron. Dig up the cache. Then head up the stairs on the right into a corridor containing several corpses and a relic (3/13), a Belt Buckle from the Athanatoi set. Continue to the next room, where you'll find the Infirmary Base Camp, a container of cloth, and a document (5/33), Last Parting from the House of the Afflicted series (Greek). Go through the open doorway into the puzzle area. (screenshots)
HOUSE OF THE AFFLICTED CHALLENGE TOMB: The codex is in the little room high up on the far side of the courtyard. To get there, you'll need to position the suspended wooden platforms on the left side of the room so that you'll be able to jump across. First, collect a few goodies: There are mushrooms growing on the right near a buried survival cache (3/20). You'll get the map clue for this one shortly, but you can dig it up now if you like. (screenshots)
Hop into the shallow pool on the right (northwest) side of the room and swim through an underwater opening into the next room, where you'll find an Explorer Satchel (2/5). Examine it to discover the locations of 3 survival caches. We already found two of these. The other survival cache (4/20) is buried just to the left of the satchel. Dig it up and then swim back to the main room. (screenshots)
On the ground below the codex room is a box containing a relic (4/13), a Necklace from the Icons of Kitezh set, a basket of herbs, and more mushrooms growing on the ground and in a dead tree. There are also several bird's nests containing feathers scattered around this area. (screenshots)
Drop down into the shallow pit to the left of the relic. Open the container for some cloth. Then stand on the wooden platform, facing the 8-shaped metal bracket, and fire a rope arrow to attach the bracket to the platform. Climb out of the pit and go around to the cart sitting under the ledge on the right (when facing the entrance). Pull the cart away from the wall as far as it will go. (screenshots)
Now stand with the entrance and the first wooden platform on Lara's left and the cart ahead on the right. Look up to spot a rope-wrapped bucket and a lever just above and to the right of the bucket. Shoot the lever with a rope arrow to pull it, opening a small hatch and causing water to flow into the bucket. As the bucket sinks, it raises the two platforms. Don't wait to watch this happen. Run forward to stand between the cart and the shelf stacked with barrels. Turn left and shoot a rope arrow into the bucket anchoring it to the rope-wrapped barrel in the cart. You need to work quickly before the bucket rises again. If you don't manage it the first time, just pull the lever and try again. (screenshots)
Once the bucket is anchored to the cart, the platforms remain raised, so you can take your time. Climb the stairs to the left of the entrance. Swing across the horizontal bars to the first hanging platform and then jump across the ledges to the second platform. From there you can reach the handholds on the wall that will allow you to climb over to the room with the codex. Before entering the room, read the document (6/33) sitting on the railing to the left. It's called Hinterlands and belongs to the House of the Afflicted series (Greek). Enter the room and find a box of supplies; more mushrooms, cloth, and herbs; an Archivist Map (2/9) revealing the locations of various items you've already found if you followed this walkthrough; and the codex itself. Read it to unlock the Fast Healer skill and gain XP, as well as 10,000 Expedition Credits if this is your first time beating the tomb. (screenshots)
EXIT TO THE VALLEY: Step back outside and slide down the zip line on the left. If you missed survival cache #3 on the left near the stairs, get it now. Exit the room through the main door to get back to the Infirmary Base Camp. (screenshots)
At this point, you could use the Infirmary Base Camp to fast travel back to the Valley Farmstead and strike out from there for the Crypt that is now marked on your in-game map. To save backtracking, I prefer to wait until we have other business in that area. So instead, follow the passageway beyond the base camp, past the relic you found earlier, to the room with the cauldron. If you missed survival cache #2 buried near the cauldron, get it now. (screenshots)
Then follow the passage to the southeast, eventually emerging from the ruins where you fought the wolves earlier. Crawl through the low opening where you first entered this area. Stand by the rope-wrapped post and shoot an arrow into the beam below and to the right to create a zip line so you can slide down. (screenshots)
Pick up the main walkthrough at the section EXPLORING THE LOWER VALLEY.
†UPDATE HISTORY: 1/9/16 - First draft of walkthrough posted online.
6/5/16 - A few minor changes made while revising the main Geothermal Valley walkthrough.
10/7/17 - Switched the numbering of survival caches #2 and #3 on the map, thanks to a correction from huddy.