The method I am about to describe is not supported or endorsed by either Bioware/EA or Microsoft. You are strongly encouraged to play the Multiplayer portion of Mass Effect 3 in order to raise Galactic Readiness, any unauthorised manipulation of your saved game files may be detected over the XBox Live network resulting in you being banned from the service. Those of you who cannot get online with your console have little to no risk because Microsoft cannot block you from a service you do not use, nor can they detect any breeches of the XBox Live terms and conditions by users who keep their consoles strictly offline. If you use the advice in this guide, you do so at your own risk, and neither the author, Bioware/EA or Microsoft are liable for any damages or loss of data that result.
OK with that, still with me? On with the guide.
Everything you need to do any form of Mass Effect 3 XBox360 save file manipulation:
Got all that stuff? OK, let's get cracking.
Preparing your USB storage device:
If you're already familiar with how USB storage works in conjunction with the XBox360, you can go ahead and skip this part and we'll meet up again in the next section. For those who don't, USB storage allows you to take files from your XBox360 and safely store them on a removable device. For our purposes, it allows you to port your save files from the XBox360 across to a Windows PC or laptop.
Unless you bought a new pen specially for this, your device probably already contains some files that you may have put there at some point in the past from your PC. Now is a good time to verify if any files exist on the stick, and if so copy them across to a folder on your computer. You'll be needing to completely wipe the contents of the USB device shortly, so make sure you make copies of all the files you don't want to lose.
When you're confident your USB device contains no data you don't want to lose, insert it into your XBox360 via the USB ports on the front or rear, and then power up your XBox360. In the Dashboard, go to the System Settings, and then to Memory. You should see at least three items in the list. Among them should be 'USB Storage Device', move down to it and select that option.
At this point, you'll either see the 'Configure USB Device' screen or you won't. If you see the screen, click 'Configure Now' - this will erase all the content on your USB device, and split the device's 'disk space' in two. The XBox360 will allocate a chunk to itself, and your Windows PC will get the remaining chunk. Don't worry, this isn't permanent. By formatting the USB device at a later point you can remove the XBox360 file system from your USB device and give your PC access to the whole pen again. Don't worry if you get a message saying your device doesn't meet the performance recommendations, as this doesn't matter and can be safely ignored.
Getting your file onto your USB device:
Before you go any further, log into the user profile associated with your Mass Effect 3 save. With your XBox360-formatted USB device inserted, navigate to the hard drive, and find your Mass Effect 3 saved game. You'll notice that the saves appear to be grouped by character, for example if your Shepard is named 'Fred' there will be a save called 'Fred - Vanguard - 2005/11/22' or something similar. If you select this, you're given the option to move, copy or delete the file.
Ordinarily I'd suggest you copy the file - but Mass Effect 3 won't let you do this. Instead, you'll have to move the file onto your USB device. This means that all your hard work only exists on the USB device and nowhere else. You'd better make a copy of that file pronto or you might make a mistake and lose it all.
Backing up your original save:
Unplug the USB device from the XBox360, and insert it into your Windows computer. You'll notice that if you browse the device in Windows Explorer the device appears to be empty... do not panic, this is normal. The reason you had to configure your USB device on the XBox is so that the XBox can build a file system on the device which Windows ordinarily doesn't know how to read. That's one of the reasons we need Horizon.
With Horizon downloaded and installed, launch the program. It takes a little while, so please be patient. If you get a message telling you that the program is operating in Offline Mode then just click OK. Eventually the main Horizon interface will appear.
To the right of the screen should be a panel called the Device Explorer. With your USB device inserted, you'll see the device and all it's virtual XBox360 folders in the lower portion of that panel. The topmost virtual folder should be 'Games'. Clicking that should expand the tree to display 'Mass Effect 3', and clicking the game's title will expand the tree to display your saved games.
Right click on your saved game, and select 'Extract File...', then choose a location to save your backup copy to, and hit Save. You've now got a fully working backed up copy of your saved game in case anything goes wrong. It's useful to perform this procedure outside of save file hacking from time to time since an average home computer generally has a larger hard drive than an XBox360, and you can even burn your saved games to DVD for an extra layer of protection. To restore the backup, with the Device Explorer panel visible in Horizon and your XBox360 formatted USB device inserted, simply drag the file from your computer's hard drive directly into Device Explorer. Horizon is smart enough to know where to put it, so don't worry about remembering which folders things came out of.
Extracting your saved game from your career file:
Now, as you probably noticed - you may have several saved games associated with a single Shepard within Mass Effect 3, but you only saw one file when you came to put it on your USB drive. This is because the file you have on your USB device is basically a career file. An archive (think of it like a ZIP or RAR file) that contains multiple files, which in this case are your actual saves. Career files are not supported by WinZip, WinRAR or any other regular PC archiving utility, so you'll need Horizon again to get at these files and extract one.
Find your Mass Effect 3 save file within the Horizon directory tree in the Device Explorer, and double click it. The Device Explorer panel will vanish and you'll get a small window in the middle of the screen with your career file as it's title. You'll also see a lot of data, numbers and buttons that look quite scary to newcomers. Don't worry about these - you won't need to touch most of them, and if you make a mistake you can always just restore the backup copy of the career file you made earlier (you did make one, didn't you?) to your USB device to get your file back to it's original state.
Now, click where it says 'Contents'. This will change the window to show all the different save files that are contained in this Shepard's career save. If you can see all your actual saves here, as well as your autosaves and chapter saves (and even new game plus for some reason) you're all good to go. You'll easily recognise your most recent manual save here, as it's the one with the highest number in the filename. Select it, right click it, and then select Extract. You'll be asked for a location to save your file, so find a good directory to store it in and hit Save.
At this point, I'd recommend backing up this file too - so use Windows Explorer to create a copy of the file somewhere just in case.
Extracted the file? Got a backup of your career file and saved game somewhere? OK, let's edit.
Editing the save file to increase or alter War Asset values:
Horizon can't do this, but you may as well leave that window open as it will save you time since you'll need it later. For this part of the process, you'll need to fire up Gibbed's Mass Effect 3 Save Editor for PC and XBox360. You can launch this directly by double-clicking the EXE file within the archive as no installation is required.
With the main interface open, you'll need to get your save file in there. To do this, click Open and find the saved game you extracted earlier. This is the file that has the extension 'xbsav'. There are three tabs in the main interface - Player, Plot and Raw - if 'Raw' is not selected, click it. You'll get a seemingly long list of data displayed. Again, this can be scary, though much of it is obvious and easy to figure out. You don't absolutely need to touch much of this, but if you feel like it explore away.
What you really need to do is go down to the bottom of that list, to where it says 'Player'. It should literally be right at the bottom of the list. This will expand the tree with more items that appear underneath, one of which should be 'GAW Assets'. Find and click this, and then click the tiny button that appears to the right of this line that says '...', to gain access to the GAW Asset Collection Editor.
This bit is a little strange. There are no names displayed for the assets, only numbers. This is why I included 'Diana Allers' in the requirements list. She's referenced in the editor as asset number 186. You'll need to scroll down the listbox until you see a '186' appear - not the 186th item, but the item that is called 186 - and then click it. If you've never edited your save file before, you'll see that she has 5 strength. If she does not, either you've clicked the wrong item (look again, make sure you have the list item with the name '186' selected) or you previously edited the file.
When you're sure (or confident) you have the right item selected, you can manually edit the Strength value. This alters the number of points that the 'Diana Allers' GAW asset brings towards your total. You can make this as high or as low as you like. When you're done, hit OK to close the GAW Asset Collection Editor, and return to the main interface. From here, you can simply click Save (at the top of the screen) to save a copy of your modified save file. You can then safely close Gibbed's Mass Effect 3 Save Editor.
Injecting your modified file into your Shepard's career file:
If you kept your Horizon window open, you're most of the way there already. If you didn't, follow the steps in the sections above to bring up the list of your career file's contents. What you need to do now is right-click on the save file you extracted earlier, and choose 'Replace' from the popup menu that appears. Find your modified save file in the dialog you're presented with, and hit Open. Finally, click the big red 'Save, Rehash, and Resign' button. This will modify the file so that your XBox doesn't detect that it's been tampered with (which is essential otherwise the file will show up as corrupt on the XBox360), and also directly saves the whole career file back to your USB device. You can now close Horizon.
Moving your modified career file back to your XBox360:
Unplug your USB device from your computer, and insert it back into your XBox360. Navigate to your Storage Devices, and then to Memory Unit ('USB Storage Device' becomes 'Memory Unit' when it contains a XBox360 file system), and you should see your Mass Effect 3 save file present and correct. If everything went well, select the Move option to transfer it across to your XBox360's hard disk drive.
Verifying your edit worked:
Now it's time to see the fruits of your labour. Launch Mass Effect 3, and manually load the correct save file from among your Shepard's career saves. Hopefully you were sensible and saved on the Normandy, if you weren't... you'll have to get back there ASAP. Head to the War Room and check out your GAW Assets.
You'll need to find 'Diana Allers', she's tucked away in 'Alliance'. If everything went well, her value should have altered from 5 to whatever value you changed it to within the editor. You may even notice that - providing you changed it significantly - your blue/green EMS bar will have updated to reflect the change. With a boosted Allers, it's much easier for a single-player only player to obtain the maximum EMS.
Why did I choose Allers:
Just in case you get a touch guilt-ridden over adjusting your EMS in this way, you'll be pleased to know that as long as Allers carries the burden of all your alterations - the status quo can be easily returned by simply booting her off the ship. It's true that you can always edit her values back down to 5 again and that kicking her off the ship would actually cost you those 5 points, but you always have both options so you can pick a method as you see fit at any stage down the line.
And besides, if you're going to carry her around with you on the Normandy, this at least makes her a more valuable asset.