Argul’s Tomb is about the tale of an older Dead King than the Lord of Bones. His name was Argul, and he was betrayed by the current Dead King for the sake of his throne. This walkthrough covers the Frostbone Crypt.
You’ll find the burial site in question to the south of Ostegoth, and you’ll need the Voidwalker to get there. Once you’re in, you’ll see a statue.
Go west from it and follow the path south as there will be a gate blocking your progress. Continue this way until you enter a room with corruption crystals (the yellow stuff) in a corner. On the western side of the room, you’ll see a portal and a Death Grip hook.
After activating the portal and head down the stairs in the northeast corner of the room. You will come to a giant gap in the floor, but you will be able to see another portal across from you. Activate it and return to the first portal you activated. Use your Death Grip to scale the wall and into the portal.
You’ll pop out the portal on the other side of the gap. You’ll also find another portal you need to activate on the northwest corner of the room, activate it, then use the portal behind you once more to find a shadow bomb. Behind you, (above the portal you just exited) you’ll find a hole in the wall with another portal.
Activate it and throw the shadow bomb through the portal you last used. It’ll land on the corruption crystals. Blow them to hell and continue your merry way unimpeded.
After running along the wall you’ll find yourself in a circular room where enemies will swarm you. Get rid of them and pass through the door, bringing you to the other side of that gate. Open the nearby chest to grab a skeleton key and then pull the lever opposite it to open the gate, now you can head back to the statue with the missing lantern we saw earlier.
Head south from said statue and you’ll enter a room with a broken bridge and the glowing green lantern you need to acquire will be across the gap. Behind you is a portal, to the east is another. Activate both and walk through the one behind you.
Follow the path you see to the end and find another portal on the far left wall across a large gap. Activate it with a charged shot and walk back into the portal you just emerged from to be shot against the wall and proceed to pull yourself up onto a ledge.
There will be a new portal in front of you, so activate it. Then turn around and face the north, looking up a little bit, and you’ll find another portal behind a couple of hanging wooden beams. Activate it with another charged shot and walk through the nearby portal to be shot out onto the wooden beam.
Rotate yourself so that you’re on the opposite side of the beam and jump backwards to reach another one. Repeat this and you’ll find yourself on a new ledge.
Follow the hallway you find, and you’ll see that a large chunk of the left wall is missing at the end. Through this hole, you’ll see a portal towards the bottom right. Activate it and trek back to the previous one. Go through it and you’ll see some more beams you have to run across and eventually pull yourself up onto a ledge.
Follow this straight-forward path through the circular room of enemies, kill them, and you will find yourself on the side of the broken bridge with the lantern. Activate the portal on the side you’re on as well as the one on the far side of the bridge, grab the lantern and walk through the portal. Return it to the statue.
The statue will be pointing at a deactivated portal, activate it, and then use the portal you came out of back near the broken bridge.
Head down the hallway on the western side and activate the portal which will be to the right when you reach the end of the floor. This will unlock a door you walked past while trying to open up the gate when you first arrived.
Follow the linear path until you reach an open room with some destroyed stairs in front of you and number of enemies below you. If you turn to your right as you enter and climb the stairs, there is a chest nearby you can loot. After that, jump down and fight your way through the enemies and the Frostbone Giant.
After you kill the giant, you’ll receive a Spire Key. There is a chest you can open along a small path which will be shown on your mini map, and after you open it, exit the dungeon through the portal which has just been created on the floor. I think I’ve had enough of portals to last me a lifetime now.