###Heart of the Mountain puzzle and Ascend the Cave Shaft
You are going to find that you are currently in a very large room that is packed full of ancient machinery as well as a number of different mysteries and riddles. Your mission right now is to reach the highest point possible, so cling to the large wheel that is located in the orange lantern light on the right side.
When you interact with it, Atreus will mess it up for you. Instead of calling down another lift similar to the one outside, he destroys it, ensnares the large chain, and draws a significant amount of attention from the Draugr. Take care of business with them! Be wary, as these will now glow and explode when they are approached, which can create a hazardous situation.
After you have vanquished them, you will need to devise a strategy for untangling that massive chain.
###Free the Chain
Okay, so there are a lot of things to investigate around here, but it’s not necessary to take care of all of them right away. You will need to return at a later time to access the Hidden Chamber, which is located in the region that is overgrown with Hel’s bramble and contains more of that red sap.
The two most important things for Atreus to do right now are the following: first, there are some runs written on the back of a grounded mine cart that is located in the middle of the room.
In addition to that, there is a chest hidden behind a breakable wooden wall that is located to the left of the entrance that was just opened where the Draugr came from.
Now, proceed further down that recently opened tunnel, and of course, you will come to Brok! You should make use of this opportunity to purchase or improve anything, and then proceed.
First, ascend the wooden panel that has a gold marking just to the right of Brok until you reach a ledge with a chest containing hacksilver, a large healing crystal, and a slope that leads back down to a coffin chest containing additional solid Svartalfheim Steel. The slope is located on your right.
You’ll find another one of those spinning panels just above the spike trap, to the right, if you jump back down from where you were and continue forward to the left.
As you have done in the past, hurl your axe at the panel that has a yellow marking on it. This will cause it to spin, gradually removing the spikes. Perform this task until the panel will no longer spin, at which point you should dash through the obstacle, and you should be fine.
Hit the yellow panel in the corner to open the next door, and then get ready for another skirmish with a variety of Draugr in the room that’s ahead of you.
You now have another puzzle to solve, but fortunately, almost everything in the room can be collected at this point, so that’s a plus.
Your objective in this area is to push the massive mining cart through the large gate after you have opened it on the left side of the room as you enter it. You need to go to the mining cart that is directly ahead of you and grab it in order to pull it towards the gate. However, you will find that it is still attached, so you will need to quickly hack at the glowing disc that is attached to the rope in order to continue dragging it across under the left hand drawbridge.
Before proceeding upward, there are two tasks that must be completed on the ground level after the object has been moved to the left. First, move behind the large creature that used to be the cart’s puller, and you will see a load of loot lying on the ground (this may have been the result of killing a small wild purple lizard that was running around, but for us it was just loose loot!)
Then, look at the location where the cart used to be; you’ll find another one of those spiked doors there, which you’ll need to open with your axe, and an Artifact within it.
Now you need to climb up onto the raised platform that is located above the mining cart and then onto the raised platform that is located above that. You should first investigate these upper areas by striking the glowing discs that are holding up the two sets of drawbridges. After that, you can proceed with raising the gate and going further.
After crossing the first bridge, descend through the hole to retrieve the key to the coffin chest, and then return to the starting point by climbing back onto the cart and crossing the second bridge.
Now make your way to the opposite end of this elevated platform, taking out the Draugr along the way, and then eliminate the Odin’s Raven that is positioned directly in front of you.
Hit the discs in the same manner as before to bring down the second drawbridge, then cross the gap and deal with the remaining Draugr. Finally, fire at the Crystal to generate some light and expose the two ledges that are immediately adjacent to it. You’ll find another coffin chest if you climb up the ledges to the south.
Proceed into the next room after lowering yourself down the opposite side, which will bring you back to the spot where you initially climbed up from the cart (the one where Atreus broke the lift).
After making your way through the torchlit tunnel and destroying the wooden barrier that stood in your way, you will emerge on top of one of the raised platforms that are located on the other side of the gate. You can now pull the chain that is located there to raise the gate, and then you can cut back to the cart more quickly by going through the smaller gate that is located just next to you.
After pushing the cart through the gate and positioning it so that it is parallel to the platform you were standing on, you can then hop up onto it. You can make the jump to the east ledge now, where there is a legendary chest waiting for you just ahead.
You need to make your way to the opposite end of that platform, raise the massive bouler that’s holding the chain in place, and then get ready for a fight…