The Harvester is exclusive weapon for Xbox360/PS3 versions of the game, and essentially an upgrade to Scythe with extra souls harvesting (+10% souls for each kills)

in Darksiders: Warmastered Edition (which you receive for free for buying this game) player may purchase The Harvester for 5,000 souls from Vulgrim, however in original Darksiders game player has no option to get that weapon which may trigger some OCD-people and those who are doing achievements-run (because extra +10% souls are handy)

thankfully, The Harvester is still present in Darksiders and you may easily unlock it via save editing

credits:
during that guide you will use WAR tool from John Simon (@whatisaphone). it is an open-source save-editor program for Darksiders and Darksiders: Warmastered Edition

link to repository: GitHub[github.com]
author: @whatisaphone[github.com]

>>> MAKE BACKUPS <<<

(1) play Darksiders as usual and buy Scythe from Vulgrim (if you already got Scythe, then skip that step)
(2) save your game into the first slot after auto-save slot
(3) download that archive. it has tools for unpack/packing savefiles

https://drive.google.com/file/d/1BjB2kzKrv11Qe80vqjkdoRvGtHwGI99E

(4) unpack archive's content into the folder
(5) launch the file "unpack.bat"
(6) a new file named "dssave0.json" will appear. open it with any text-editor
(7) search for the line
(8) and replace it with
(9) save "dssave0.json" file
(10) launch the file "pack.bat"
...and that's it. so basically, save game into the first slot, use tools to unpack savefile, edit one line, use tools to pack savefile back


The Harvester correctly works with "Battle Hardened" achievement, because game checks for exp-level per Object's instances, not per its actual values. so it checks like this (I have tested it):

instead of, say, this:

but given how finicky and broken achievements in original Darksiders, you may fool-proof yourself by reverting The Harvester back to Scythe once you start grinding for "Battle Hardened"

one way or another but it is pretty much impossible to have full-leveled Scythe/The Harvester before end credits without dedicated grind. so you may play the whole game with The Harvester, get Armageddon Blade, then change it back to Scythe and complete "Battle Hardened" achievement. but once again, this is not necessary because of how game handles its data and triggers

and as an extra bonus there's some raw data on how various items affect gained souls:

if enemy drops less than 100 souls by default:

if enemy drops more than 100 souls by default:

if you want to thank me...

...then check my guide about fixing various game issues: launching, crashing, optimization, stuttering, gamepads, etc. the guide is huge, but the topic is broad to begin with
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1935376439