As I have said in my other solutions, make sure to have the difficulty turned right down and to save regularly.
You need to complete two quests to reach this rank and unlock the achievement. Retaking the Fringe and Rebuilding the Gatekeeper are those two quests.
First you must travel to The Fringe, do this by fast travelling to the gates and then going through them. On arrival, you will notice that the place has been taken over by the Knights of the Order. Head down into Passwall and speak with the commander of the Golden Saints (it will be Saints if you have followed my previous solutions), Aurig Desha. She will talk about the Order and then you are given the option to take control of the remaining troops or let her position them. It is best to just let her command them. When this conversation is over, you will experience a few waves of Knights. Kill them all until you are told to speak to the commander again. When you talk to her, she will tell you that you need to deactivate the Obelisk in Xeddefen. This area is absolutely filled with Knights but you should be fine providing you have the difficulty at its lowest. Make your way through the ruin, dealing with the enemies. On your way, pick up some Hearts of Order by looting the dead bodies. You will need 3 when you get to the Obelisk. When you get to the Great Chamber, you will find the Obelisk in the centre, make your way to it and place the hearts you picked up inside it. When you have placed 3, it will deactivate and the ruins will start to collapse even more. I suggest saving regularly along here as any flurry of falling rocks can easily kill you. If the screen starts to go sort of fuzzy, blurry, just wait and let the rocks fall before moving forwards. You will find that on the way out, most of the gates you come across will be shut and you need to hit those little green buttons to open them which is annoying. When you get out of Xeddefen, speak with Desha and she will tell you to go and see Sheogorath. Head back through the gates and fast travel to the castle.
Sheogorath will set you with a new quest; that of rebuilding the Gatekeeper. You need to travel to Xaselm in search of Relmyna Verenim (remember her) to find out more about doing so. When you get to her after making your way through the caverns, she will task you with finding certain objects to help create this new Gatekeeper. She is reluctant to help at first but keep with the conversation and eventually she will give in. You now need to go to the Gardens of Flesh and Bone to collect these items. The paths here can be quite a maze but I found that if you ever get lost just follow the streams of green gas. The markers on your map normally do the job but the little green streams helped me find the Breath. Once you have all four items, head out of the tunnels and back to Relmyna. Fast travel to her secret back entrance and go and see her. She will ask you to choose body parts for the new Keeper. I just chose random parts as I wasn't bothered about any special items for my character. If you are going to be playing the game a lot afterwards then you should research which to choose. Take the parts back to her and she will ask you to meet with her at the Fringe. There, you will find the ability to add items to the Cistern. Keep pressing A until all of the body parts and the 4 other ingredients have been added. When the ritual is over, speak to Relmyna and she will give you a Summon spell. You can then head back to speak with Sheogorath.
8 of 10 achievements done.
