Find a Way to Defeat the Bear

Right at the beginning you earn +150 XP. Follow the path back to the beginning. Here you can scramble up the wall at the wooden board and reach some ledges you can climb. At the top head into the passage.

Find Mushrooms for the Poison Arrow Upgrade

Once you enter the passage you get +50 XP. On the left you can spot some poison Mushrooms you need to collect. Run towards the climbable ice wall and scale it using the axe. At the top you will find a Salvage crate on the left and above your head a nest you can shoot down to gain Feathers erhaltet. (It's likely that the nest falls over the edge. In that case you need to collect it below.) Sometimes you can find a second nest with Feathers just next to the salvage. Use the rope slide to return to the Mongolian ruins. From here head to the north, so a little to the right from where the rope slide drops you off, back to the spot where we explored a cave earlier. In the passage you can find several Mushrooms. Once you've collected all three that were needed, you gain +50 XP.

Find Cloth for the Poison Arrow Upgrade

Now you need to find cloth, of which you most likely have one left over from the previous crate. There may be a crate with Cloth by the two fir trees near the stone circle, or by the monolith. Remember: The survival instincts will show you an objective beacon. Press RS, the right Stick button. You will gain +250 XP, if you've also collected cloth.

Return to the Camp to Upgrade Arrows

Return to the base camp Wilderness Refuge. Right of the base camp you can find a tall tree stump with Mushrooms which Lara pries loose using the axe. Sit down at the camp and enter the inventory menu, here you choose ammunition to craft Poison Arrows. When you leave the menu, Lara will retreat into her shelter for the night. After the cut scene, Lara is sitting on a tree branch. Below her is a Trinity Soldier, that can be attacked from above with the axe (press Y). Press Y again to perform a finisher with the rock Lara has picked up. Quickly hide in the bushed right in front of you, as the next Trinity Soldier is approaching. Once he's come closer, you can use the axe (pressing Y) to finish him from the cover. If you manage to get him before the stops talking on the radio, you earn the achievement One-Sided Conversation.

Sneak or Fight Past the Trinity Soldiers to Reach the Cave

Now return towards the ruins. The area is teeming with Trinity Soldiers. You can sneak past them or decide to take them down. If you want to finish them, I suggest you take them down with headshots from the bow or silently from behind to avoid a big fire fight. Poison arrows can also be useful, especially since they can take out more than one enemy at once. After you have dealt with the Trinity forces, return to the Mongolian ruins. Before you continue, you can collect more resources, if you like. Now once again climb up the tree to reach the higher level that leads to the bear cave. Collect the Salvage at the end of the passage on the right and grab the Hardwood right next to it. Once you reach the clearing, you are awarded +50 XP.

Defeat the Bear

Now it's time to deal with the bear. Approach the cave mouth. Right of it you can find a crate with Cloth. Make sure you have crafted poison arrows, then enter the cave, on your way you can find two sets of Mushrooms in the narrow passage. You will encounter the bear inside.

Combat Details

Immediately shoot it with a poison arrow. (You aim with LT and the right stick, but shoot with RB instead of RT to use the special arrows.) This will stun the bear for a moment, giving you enough time to shoot it with as many arrows as possible before it starts moving again. (Remember: Charged arrows do more damage, but they take longer to shoot. You need to find out which works best for you. I usually don't charge my shots against the bear and use up to six arrows per stun phase.) When the bear snaps out of being stunned, use another poison arrow to stun it again. And repeat shooting it with regular arrows. But leave a little time to craft new poison arrows (using RB when not aiming) before the bear starts moving again. A third poison arrow should do the trick and finish the bear. When it gets too close, run from the cave, out onto the clearing. Remember to evade its attacks with B.

Beating the bear will award you +100 XP.

Explore the Cave to Find an Exit

Loot the bear to get the bear hide, and the "Survivor Pack" card pack. Inside the cave you can collect a few more things. Now examine the back wall between the strongbox and the document. Use the axe to pry loose some of the bricks and create an opening. Step through into the passage behind and follow it to reach an ice plateau of the Glacial Cavern. You'll get +50 XP.

Follow the Mongolian Path and Search for Signs of the Lost City

In front of you, on the left, is a climbable ice wall, but since it will crumble under Lara's weight, you might as well slide down right away. Follow the icy passage down into a water cave. On the way Lara will have to crouch down. Now get into the water and learn how to dive. Dive under the stone arch and resurface on the other side. Here swim to the fork. Now dive through the stone ark and quickly to the safe shore. Here you will find the next base camp, Mongolian Passage. You'll get +10 XP for discovering the camp site. When playing on Survivor, the camp is inactive and you have to build up a camp fire by using three pieces of hardwood with X. You'll most likely have another skill point to use and enough salvage to upgrade your bow or your axe. Right next to the camp you can find a box with random resources. Now head up the ramp on the left. Jump through the water curtain (which is probably less noticeable on the 360?) into the next passage. Here you will get the notice that an optional challenge tomb is nearby. We will of course check it out, when we come past the entrance. Step forward to reach the edge and jump to the next ledge. Pull up and walk along the narrow path. Lara will spot an ancient war galley stuck in the ice wall. Jump towards the climbable ice wall and scale it, using the axe. At the top head to the right, into the next part of the cavern. Scramble up the wall ahead and follow the path upwards to the left. You will automatically slide down a chute. Run further ahead. You would have come from the right, had you ignored the challenge tomb. So we will now turn left. Jump towards the climbing wall and attach the axe. Climb to the top. Follow the path into a large cave. Here you jump to the second part of the walkway and pull up. Also jump to the third section where you also have to pull up. On the right you will find some Coins (+2). Head into the narrow tunnel and at the end get into the water. Dive through underneath the low ceiling and quickly to the end, where you can climb out of the water. Run further along, up the path. Scramble up the wall and at the top run across the narrow ledge. Through the tunnel you will reach the Soviet Installation. Head towards the base camp.