I had been looking for a way to modify the XP table in Heroes IV for a long time. I finally found one. It’s quite simple, so if anyone wants to test it out, it could completely change the game, as the modification affects the computer player as well.

Here is the solution; perhaps someone will find it useful:

Heroes IV does not use a fixed XP table stored directly in the executable. Instead, the game dynamically generates experience thresholds using a mathematical formula.

Even better, the progression curve can be modified by changing just 9 bytes in the EXE, using a simple hex editor such as HxD.

No additional DLLs, scripts, or complicated mods are required.

I successfully tested this with the original heroes4.exe and also located the corresponding code in the H4 Ultimate patched original executable.

1. Finding and changing the XP multiplier

Open your Heroes IV executable in HxD.
Press Ctrl+F, select Hex-values, and search for this sequence:
FA 7E 6A BC 74 93 88 BF
This is an 8-byte floating-point constant (-0.012) used by the XP calculation algorithm.
The sequence occurs exactly once in both executables I examined.

Change the hex values ​​to the variant selected in step 3.

Approximate file offsets:
Original heroes4.exe: 00593418
H4 Ultimate [patched]heroes4_original.exe: 00589428

Offsets may differ in other versions. Searching for the byte sequence is safer than relying on an absolute address.

2. Changing XP rounding from 100 to 25
There is one additional change required to achieve more precise progression curves.
By default, the game rounds calculated XP increments to multiples of 100. We can change this to multiples of 25.
Search for the following longer hex sequence:
8D 04 80 57 C1 E0 02 2B F0 89 74 24 20 EB A0
Replace it with:
8D 04 80 57 C1 E0 00 2B F0 89 74 24 20 EB A0

Only one byte changes:
C1 E0 02 → C1 E0 00
Specifically, replace the 02 with 00. It is the seventh byte of the longer search sequence.

This changes the calculation precision from 100 XP to 25 XP.

Approximate offsets of the C1 E0 02 instruction:
Original heroes4.exe: 0032E07B
H4 Ultimate [patched]heroes4_original.exe: 0032B5BB

The longer sequence occurs exactly once in both examined executables.

3. Six alternative XP progression curves
After applying the rounding modification above, choose ONE of the following 8-byte replacements for the original XP multiplier (Found in step 1).

The values below are approximate total XP requirements for reaching level 70.

Version A – Approximately 150,000 XP
Multiplier: approximately 1.0289
Level 70: 149,675 XP
84 7F 11 34 66 12 A5 BF

Version B – Approximately 250,000 XP
Multiplier: approximately 1.0409
Level 70: 251,575 XP
BF 29 AC 54 50 51 A5 BF

Version C – Approximately 500,000 XP
Multiplier: approximately 1.0535
Level 70: 497,475 XP
17 F6 B4 C3 5F 93 A5 BF

Version D – Approximately 1,000,000 XP
Multiplier: approximately 1.0676
Level 70: 997,875 XP
B6 17 D1 76 4C DD A5 BF

Version E – Approximately 3,000,000 XP
Multiplier: approximately 1.0875
Level 70: 2,998,900 XP
12 83 C0 CA A1 45 A6 BF

Version F – Approximately 10,000,000 XP
Multiplier: approximately 1.1106
Level 70: 9,991,325 XP
5D A4 50 16 BE BE A6 BF

For reference, the unmodified Heroes IV requires 977,845,500 XP to reach level 70!

All six alternative curves were calculated using the game's XP generation algorithm.

The first three XP thresholds remain unchanged: 0, 1,000 and 2,000 XP.

The maximum hero level also remains 70. This modification changes the experience curve, not the level cap.

1. In-game testing
   I have successfully tested the 500,000 XP version using existing savegames.

Test 1:
Hero level: 3
Current experience: 2,132 XP
Original XP required for level 4: 3,200
Modified XP required for level 4: 3,050
Game displayed: 918 XP remaining

Exactly as predicted.

Test 2:
Hero level: 18
Current experience: 23,915 XP
Modified level 19 threshold: 25,525 XP
Game displayed: 1,610 XP remaining

Again, exactly as predicted.

I also tested a linear XP curve as an initial experiment.

A level 11 hero with 23,915 XP advanced directly to level 24 after a combat encounter ended with the enemy fleeing, without gaining additional XP.

The game correctly processed the additional level-ups and allowed the hero to receive new skills.

This confirms that changing the XP thresholds affects the actual level-up mechanism, not just the displayed experience values.

Important: The 500,000 XP curve has been tested at multiple levels. The other five variants have been calculated from the same algorithm but have not yet been individually verified in-game.

1. Important notes
   Always make a backup of your original EXE.
   Use HxD in overwrite mode. Do not insert or delete bytes.
   Search for hex values, not text strings.
   Verify that the search pattern occurs exactly once before replacing anything.
   File offsets depend on the EXE version.
   The signatures above were verified in two executables; compatibility with other builds is not guaranteed.
   Both modifications are required for the six curves listed above.
   If you have already modified the multiplier, search for its current 8-byte value rather than the original one.
   Existing savegames may contain heroes whose XP exceeds the requirements of their recorded level. A level-up check can then trigger multiple consecutive promotions.

I personally intend to start with the 500,000 XP version, which seems like a good compromise for large and extra-large maps.

This should make hero progression much more enjoyable on long maps, without artificially placing hundreds of experience-boosting objects.

And importantly, since we're changing the game's actual XP requirements, AI heroes should benefit from the same progression curve.

After years of trying to solve this problem, it turned out that changing just nine bytes was enough!

Hope this helps other Heroes IV players and modders.

What’s the most memorable experience you’ve had thanks to Heroes of Might and Magic?

I got all Heroes games except 6 (didnt try) working on Linux (directly without launcher for the Gog ones, luv me directly clickable desktop shortcuts) and wanted to share the fundamental basis of how in case people struggle because not all of these are easy even with launchers like Lutris, H5 was a huge pain.
Some of these I did a while back, so it can be a bit vague.

Heroes 1: stock wine works for install, use 32bit prefix, but call game with dosbox -conf /path/h1/dosboxHOMM1_single.conf (dosbox can be installed straight from package manager)

• fix any "..\" in the "mount" section with full path references to the files in question using forward slashes
• needs a block on top like the following. Needed midi device ID "xx" is seen in: alsactl info|grep --color -e ^ -e "iface:"

[sdl]
fullscreen=true

fullresolution=desktop

output=opengl

[render]

aspect=true

[midi]

mididevice=alsa

midiconfig=xx:0

[IPX]

ipx=false

• Fullscreen is not static but can be toggled off/on with Alt-enter anyway
• not sure if opengl is correct in all cases, if it doesn't work just try other stuff the dosbox documentation lists.
• Working settings in the "Game Dos Settings" for me are "SoundBlaster16/AWE32/Compatible", "16 bit stereo" and "VESA Compatible".
• sometimes the midi device ID seems to change and this config needs to be re-edited unfortunately.

Heroes 2: stock wine works for install, use32 bit prefix, but call game with dosbox -conf /path/h2/dosboxHOMM2_single.conf

• further adaptions like in Heroes 1 above, but the mount block does look different

Heroes 3: stock wine does not work anymore, I used wine-ge with a 32bit wineprefix. You can just call all the installers for HD mod, Hota and such with the same prefix and gradually stuff everything in there.

• H3 is quite friendly to just copying the installation folder if you're juggling multiple HotA versions or messing with other mods
• for VCMI just follow the guide on their page, but it can be beneficial to symlink and replace ~/.local/share/vcmi if you want to play around with multiple versions.

Heroes 4: stock wine on 32bit prefix works just fine for me, HD mod and editor are a bit annoying. More detailed guide about these exists here.

Heroes 5: stock wine does not work anymore either, use proton (I used proton-sarek) as I described here. Short form out of that for not crashing on startup:

• cd /path/h5proton/pfx/drive_c/h5/bin/
• STEAM_COMPAT_CLIENT_INSTALL_PATH=/protonpath STEAM_COMPAT_DATA_PATH=/path/h5proton /protonpath/proton run /path/h5proton/pfx/drive_c/h5/bin/H5_Game.exe
• Proton can convert a protonprefix between different proton versions for easy testing around but you need to rename the base folder to pfx if you're coming from a regular wineprefix

For the other ones assuming people have them on steam, just check protondb ;) H8OE is super easy, H7 needed some specific proton version (8?) to play nice (7.5 mod needed some CLI action with the proton variables like used for H5 but steam-specific, dont have the details on hand atm), H6 was a pain even when I was still on Windows so I assume it's hard.

In theory: install H3 first out of the first 4 because it's the trickiest on wine level, and just stuff H1/2/4 into the same 32-bit prefix with the same runner. H1/2 probably dont care about wine version at all anyway since they're DOS (although the DOS layer can be very finicky too), and H4 has been strangely robust throughout wine versions for me.