GEOTHERMAL VALLEY - BATHS OF KITEZH CHALLENGE TOMB
CHALLENGE TOMB ENTRANCE - BEAR'S DEN: The entrance to this tomb is through a cave at the north end of the valley floor. It is close to the waterfall and the Astronomer's Crypt and it's marked with a BEAR icon on the map. As you'd expect, this clearing has the distinctive, barren look of a place that's been ravaged by a bear. And naturally, you'll need to defeat one in order to enter the tomb. She's big and tough, but she can be killed using the same tactics I've recommended before. Prep as many poison and/or grenade arrows as you can carry, equip your bow, and enter the den quietly. Peer around the corner to target the bear. (If you move out too far, she'll notice you.) Fire one or two poison arrows. Then switch to grenade arrows for a quick takedown, or alternate one poison arrow and several regular arrows, or poison arrows and bursts of gunfire. If the bear manages to shrug off the poison and charge at you, the bow becomes unwieldy, so switch to the shotgun and blast away. (screenshots)
NOTE: Even if you killed this bear earlier, take care when entering the cave. The bear does respawn, but I'm not sure whether the interval is scripted or random.
FLOODED TUNNEL: When the bear is dead, harvest the bear skin, and gather some mushrooms and magnesite, as well as deer hide from the bear's kill. Then use your axe to break down the crumbling wall. Follow the tunnel to a small pool. With the aid of the REBREATHER, which you obtained in the FLOODED ARCHIVES, you can swim through the tunnel into a marshy area with crumbling walls and hanging branches. As you approach the man-made archway on the far side of the pool, look to the right to spot a salvage crate sitting on a ledge. Get the goodies and then go through the archway. (screenshots)
WHIRLPOOL: Move to the edge but do not jump into the whirlpool below or Lara will drown. Watch as the water gushes out of 3 round grates on the left wall. There's a pattern: first a torrent gushes out of the middle grate, then the first and third grates simultaneously, then the middle grate again, and so on. In order to cross the twisted branches without being flushed away, you'll need careful timing. As the water from the first and third grates starts to subside, step out onto the branch and walk forward just until Lara is standing on the lighter-colored section of the branch between the first and second grates. Wait for the middle grate to gush then subside. Then move forward into the space between the second and third grates. This safe spot is also lighter in color. Finally, wait for the third grate to gush and subside, and then continue to the far ledge. (screenshots)
Scramble up the wall into the room above. On the left is the Whirlpool Sanctuary Base Camp and a box containing a relic (12/13), a Scroll Case from the Time of Adaptation set. (screenshots)
There's a swinging spike trap in the doorway ahead, which is triggered by a square button in the floor. It's possible to avoid it by jumping over the button or shooting it, but if you do trigger the trap, 3 sets of spikes swing down toward you. Quickly shoot the 3 wooden blocks holding up the spikes to disable the trap. (screenshots)
Beyond the trap, on the right, is another relic (13/13), an Ivory Jar from the Icons of Kitezh set. Have a look at it and then continue up the stairs. (The stairs leading down are a dead end but will later become the exit.) At the top of the stairs on the right is an alcove containing a document (31/33), The Aftermath from the Baths of Kitezh series (Greek). Exit the alcove and continue through the archway ahead, cracking open a salvage crate on the way. Squeeze through the gap between the dangling roots to enter the tomb proper. (screenshots)
THE BATHS OF KITEZH CHALLENGE TOMB: Dive into the pool, swim forward into the alcove to the southwest, and climb onto the wooden boat. From here you can see the codex in the next room through the bars. Turn around, stand near the rope spool at the front of the boat, and shoot a rope arrow into the beam on the far (northeast) side of the room. Now use your axe to turn the crank and move the boat out into the middle of the pool. When you get about halfway across, the rope breaks, but that's OK, since this is where you want to be. Shoot a rope arrow into the beam in the southeast alcove. Then turn the crank to pull the boat into that alcove. Jump from the boat into the raised opening on the right. (screenshots)
Drop down into the next room. (This is the room to the left of the codex room in case you get disoriented.) Swim across to the ledge on the far side. When you pull the handle with the rope coil, the grates on either side open, allowing some of the water to drain out of the room. But as soon as you let go of the handle, the grates close, and the water level begins to rise again. To lower it permanently, start by pulling the handle and letting the water drain away. Release the handle. Then quickly, before the water rises, turn around and run/jump across the wooden ledge on the right to the winch. Stand next to the winch and shoot a rope arrow into the rope coil above the handle. Use your axe to crank the winch as far as it will go. This should pull the handle all the way out and hold it there. This should permanently lower the water level halfway. Scramble up the wall and hop down onto the boat. (screenshots)
Shoot a rope arrow into the beam in the opposite alcove. Then turn the crank to pull the boat across the room into that alcove. Jump up onto the ledge at the end of the alcove to find the Archivist Map (9/9) for this area. (screenshots)
Now swim down under the archway into the room beside the boat. (This is the room to the right of the codex room.) Swim across to the ledge with the handle. This mechanism is nearly identical to the one in the other room, but this time there is no winch. In order to lower the water level permanently, pull the handle and wait for the water to drain away. Release the handle. Then quickly, before the water rises, turn around and fire a rope arrow into the spool on the front of the boat, which should still be parked just beyond the archway. This tethers the boat to the handle, but the water continues to rise. (screenshots)
Either jump across the ledges to the small opening high on the far wall. (There's a container of cloth on the second ledge.) Then drop down into the large room and swim over to the boat. Or, swim across the room with the handle, wait for the water level to rise, and swim out through the same opening where you came in. Climb onto the boat and turn the crank to pull the handle, opening the grates and lowering the water level. When you've cranked the wheel as far as it will go, it locks in place, and the water is now completely drained. (screenshots)
Now you can pick up 2 piles of gold coins sitting on the ground in the northeast and southeast alcoves of the main room. Shoot the jars of Greek fire sitting at the end of the alcove with the codex to blow a hole in the grating. (There are arrows nearby if you need them.) Enter, pick up another pile of coins, and climb onto the pedestal to read the codex and unlock Iron Grip, a passive skill that increases your axe climbing speed and agility. You'll also receive XP, plus 10,000 Expedition Credits the first time you complete the tomb. (screenshots)
EXIT TO THE VALLEY: When you're ready to go, exit the codex room and go through the archway ahead on the left. Climb the stairs At the top is a document (32/33) sitting on a shelf next to a statue. This is A New Purpose from the Baths of Kitezh series (Greek). Use a rope arrow to pull down the barrier. Return up the stairs to the Whirlpool Sanctuary Base Camp. If you avoided the swinging spear trap earlier, watch out for it now. From the campsite you can either ride the zip line across the whirlpool and follow the tunnel back to the bear cave in the Geothermal Valley, or use the base camp interface to fast travel to any other camp. Follow the main walkthrough for suggestions. (screenshots)
†UPDATE HISTORY: 2/5/16 - First draft of walkthrough posted online.
6/7/16 - Made a few small tweaks while revising the entire Geothermal Valley walkthrough, including fixing the incorrect numbering of document #32. All documents were included but I had mistakenly labeled both of the last two documents #33.
11/7/16 - Added info about disabling the swinging spike trap by shooting the button that triggers it. Thanks to G.O. for the reminder.