Install link: https://greasyfork.org/en/scripts/46824-clan-forum-downloader.
Before installing, you will need Tampermokey (https://tampermonkey.net/) to be installed on your browser.
Current public version: 1.3.3.1.

On your clan forum's page, click on the Download Clan Forum button to start the download.
Make sure that your internet connection is working correctly or else the download will be cancelled. To fix this, reload the clan forum page.
If the clan forum page or any tabs/windows that are opened are closed, reloaded, etc., the download will fail and all required data will have to be requested again by going to your clan's forum page and clicking on Download Clan Forum.

Improvements that I currently have on my to do list:

• fix pager bugs
  
• make jump to last page links on threads table?
  
• make search clan forum button
  

Feel free to request more.

Edit:
For me, it took roughly 40 mins to download 406 threads and about 1 min to download 14 threads.
The download is saved as a HTML file (a webpage).

Edited 5/20/2018 17:26:18

Sample output?

All threads:

Thread:

How can I trust someone to download their userscript onto my laptop, if they get booted on clan league? :(

Would it be possible for you to share the output as a file? I just want to get a feel for how easy it is for someone to browse a bunch of clan forum posts extracted using your system.

@knyte see
https://danwlgames.000webhostapp.com/WL_WZ/CFD/Warzone__--The_Avengers--__clan_forum.html
https://danwlgames.000webhostapp.com/WL_WZ/CFD/Warzone_%CE%91%CE%98%CE%95_clan_forum.html

Note that the Powered by 000webhost banner wont be displayed.

Edited 5/1/2018 18:48:48

This is really good quality, beats out even the manual saves did.

I can only get it to download the 25 first threads (aka, 1st page). Am I doing something wrong? Since your example have 400 threads ^^

Can you send a copy of all of the text in your browser's console?
Theoretically, nothing should go wrong unless your internet connection isn't/stopped working or you closed a opened tab or closed the clan forum tab.
Edit: were you able to save the download?

Edited 5/1/2018 23:31:04

1.1 Changes:

• gathers required clan forum data in the background and displays the progress
  
• automatically detects errors
  

Currently this doesn't work in TBest's version of Chrome for some reason. I'll try to fix this later today.

1.2 Changes:

• made it possible to cancel with / without downloading what's already been gathered
  
• made it possible to pause gathering required data
  
• fixed bug that caused the script not to work in Chrome
  
• fixed bug that caused the script to abort the download when Hide Threads and Replies by Poster is enabled
  

1.3 Changes:

• downloads are paused if your device's internet connection is too slow (more than a min) to respond - you'll have to manually resume the download
  
• made pagers that limit the amount of threads or posts displayed per page - this is an experimental feature
  
• made matching clan forum page case-insensitive
  

1.3.1 Changes:

• fixed pager labelling error
  

Edited 5/4/2018 22:08:46

error:

SecurityError: Blocked a frame with origin "https://www.warzone.com" from accessing a cross-origin frame.
Stack:
Error: Blocked a frame with origin "https://www.warzone.com" from accessing a cross-origin frame.
    at ReadThread (chrome-extension://dhdgffkkebhmkfjojejmpbldmpobfkfo/userscript.html?id=3ba019d8-97a3-4d77-9323-a80cb4d20268:1597:25)
    at HTMLIFrameElement.ReadThread.nextThread.onload (chrome-extension://dhdgffkkebhmkfjojejmpbldmpobfkfo/userscript.html?id=3ba019d8-97a3-4d77-9323-a80cb4d20268:1740:4)
Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.186 YaBrowser/18.3.1.1232 Yowser/2.5 Safari/537.36

You'll have to use a different browser :(. Try Firefox or Edge instead (only tested in these).

It does work on Yandex Browser, I successfully downloaded FELIDAE (56 threads). But I will try anyway

1.3.2 Changes:

• Fixed a range of pager bugs
  

As pagers are applied dynamically, you don't have to redownload your clan's forum for the changes to be applied. Instead if you downloaded your clan's forum with version 1.3 installed, you can copy lines 464 to 877 of the script's source, open your downloaded clan's forum in a plain text editor such as Notepad and replace everything in the <script>...</script> section with these lines. Remember to save the changes afterwards!

Edited 5/7/2018 11:35:19

1.3.2 to 1.3.3.1 Changes:

• Bug fixes.
  

I would absolutely love it if you added the ability to download mail threads/pm's and also some summarizing stats on the user(s). Like number of posts, number of characters etc. to the tool.

Was thinking someone would request PMs/certain threads to be downloadable at some point. Won't be able to get round to doing that for a couple of months because of being busy in RL. I can do stats really easily. Where should the stats be placed?thinking of placing it on the first page of a thread and clicking a satatistics button which lists the stats. Also which other stats should be included?