1. Gibbed Save Game Editor
2. A hex Editor (for Legion only)

And that's all ! Simple, isn't it ?

There are four characters to recruit after Horizon : Tali, Thane, Samara and Legion. Acquiring the three first is very easy, the latter being a bit more complex. Here we go.

After finishing Freedom's Progress and boarding the Normandy, save the game, then open the save in Gibbed's Save File Editor (it should be located in Documents / BioWare / Mass Effect 2 / Save / NameOfYourShepard_ANumber_Class_DateOfCreation)

Go to Plot => Henchman => Flags. Check two boxes :
1. Miranda in alternate appearance.
2. Jacob in alternate appearance.
It should look like this :



Save the file and load it up in your game. If it works, the game will automatically give you the "Retrain Powers" and unlock the entire galaxy map. If you want to recruit Legion first, you will have to hex edit the file twice - once for disabling the IFF, and once for enabling it - as it will be shown later.

NOTE : this will temporarily lock you out of the rest of the galaxy map and still forces you to recruit the original four squadmates (Jack, Mordin, Grunt and Archangel).

This can be done before recruiting the original four or just after : once you have recruited the post-Horizon squadmates you wished to recruit, save the game and open the save in Gibbed's Save File Editor. Go to Plot => Henchman => Flags and uncheck Miranda's alternate appearance (keeping Jacob's checked).
It should look like this :



This will lock the galaxy map again and enables the trigger for Horizon.

After Horizon, there is a five mission counter before the Disabled Collector Ship mission. So, what's best is to do the following instructions just after Horizon, so you've enough missions to trigger the Disabled Collector Ship : save the game, then open the save in Gibbed's Save File Editor. Go to Plot => Henchman => Flags, check Miranda's alternate appearance and uncheck Jacob's alternate appearance. This will enable the Disabled Collector Ship mission.

It should look like this :



After that, the game should run normally. It may require extra work, but it's worth it !

Recruiting Legion early is a bit more complex, as it messes up the main Collector questline.
FM's note : I never did this personally and the links towards the illustrations were dead. Sorry if this part is not clear, I did my best.

IF YOU DON'T WANT TO RECRUIT LEGION EARLY, IGNORE ALL THIS SECTION !

After you recruit Legion, the game forces you to take the IFF. According to Ecael, even teleporting to the Reaper Core immediately doesn't fool the game : it still assumed he picked the IFF up. Here's how we do it. First, simply play the mission to recruit Legion. After that...

There are two values to need to change : one controls the IFF two-mission cooldown (before the crew's abduction) and the others controls the main "Stop the Collectors" quest. The "Stop the Collectors" quest relies solely on the list itself ("Assemble the Team") and not the mission description on the fight side.

Do a backup of your save. Then, open the save file with your Hex Editor.

1) IFF countdown - Search for a text string called "None.É" (quotes excluded) Starting from the N, skip an A6 amount of blocks (166 blocks in decimal format - sorry, there's no similar starting area for other save files!). The few blocks before it should look something similar to E4 84 0E (ignore this even if different). The next block is 01 (IFF installing). Switch it to 00 to disable it.

2) Stop the Collectors mission - We're not finished yet, we still need to modify the mission log. Do a search for 7E 14 00 00 or 9A 18 00 00. That 7E 14 is actually one quest ID in reverse (the real ID is 14 7E = 5246, which Ecael believed to be the Prologue quest). The list after that is all the quest IDs currently in your mission log. The important part we want is before that, which keeps track of your quest progress in order that you receive them.

Normally, the Stop the Collectors quest is listed under 0A (10th Quest). and then has a whole bunch of zeroes after it until 0B. However, if you have the Kasumi and/or Zaeed DLCs installed, it may be after 0B or 0C. What you need to search is the 05 00 00 sequence. It tells the game to skip from "Assembling the Team" to the "IFF installation".

Let's say you've found the 05 00 00 sequence between 0A and 0B. Copy and paste this string, overwriting 0A up until before 0B and changing the file's size :
0A 00 00 00 01 00 00 00 01 00 00 00 00 00 00 00 --(before 0B)
(If you've found it between 0B and 0C, then you will have to overwrite 0B up until before 0C, and same with 0C and 0D)

Save the file, and then OPEN/SAVE IT IN GIBBED'S SAVE EDITOR to renew the file checksup (otherwise, the game will detect it as corrupted)

This changes it back to "Assemble your Team" and Kelly won't start jabbering about missions you haven't done yet. You can now play until you want to enable Horizon yourself.

The following instructions should be done only when you're ready to have the Normandy crew abducted. In other terms, any time after you've completed the Disabled Collector Ship mission, preferably.

It should require you to do at least two missions before triggering it. So, before doing this, make sure you still have two missions left to do.

Again, do a backup of your last save, then open it with your hex editor.

1) IFF countdown - None.É area, starting from N, skip A6 amount of blocks (166 blocks in decimal format). The next block will probably say '40', switch it back to 01 to install it:

2) Stop the Collectors Mission - Do a search for 0A 00 00 00 00 00 00 00 to make life easier (if it's not 0A, it should be 0B or 0C - the same you had to edit before).

The 05 comes just after that (and the 04 at the end before 0B - or 0C or 0D, you know how it works now) is essentially saying "Go get the Reaper IFF" even after you already completed it. Time to change that.

Let's say, as before, you've found the 05 between 0A and 0B. Copy and paste this string over 0A and before 0B:
0A 00 00 00 00 00 00 00 06 00 00 00 00 00 00 00 01 00 00 00 02 00 00 00 03 00 00 00 04 00 00 00 05 00 00 00


Save the file, and then OPEN/SAVE IT IN GIBBED'S SAVE EDITOR to renew the file checksup (otherwise, the game will detect it as corrupted)

That should trigger the IFF installation almost immediatly (or with two missions done). You can now go through the Omega-4 relay after this and finish the game normally.

Some weird facts can happen when doing this.

- Kelly might start talking about missions you haven't done (especially the collector ship). She shouldn't do it too much though (I did recruit Tali early three times, and Kelly only mentioned the collector ship, then went back as normal).
- Lair of the Shadow Broker and The Arrival DLCs might trigger and stay activated when you get back to the pre-Horizon state. It will not prevent you from completing the DLCs normally though.
- You will get the "Retrain Powers" research earlier. Not a big deal.

There might be some other issues, but I didn't experience them. If you do everything right, you shouldn't have trouble finishing the game. If something bad happens, leave a comment and I'll do my best to help you.

And remember to backup your saves, especially the ones you edit with the hex editor !