IcyNapalm: Okay, it's sent!
Alright: good news/bad news time.
The bad news: I'm sorry but I can't edit the blade into your file. I tried for almost hour and I officially give up. Unlike the previous edition, the saves in HoMM3 Complete are zipped and it appears encrypted, so I can't edit them. Tried all possible ways. After that I tried loading the game and editing the memory, using the guide here:
http://heroescommunity.com/viewthread.php3?TID=18817 but it didn't work. Not sure if it isn't outdated but I just couldn't find those addresses. And I searched for all various possiblities (artifacts, units, primary stats, XP).
Sorry about this :(
Now the good news:
_You DON'T need Armageddon's Blade to finish the game. If you capture all enemy cities and kill all heroes, you will win the level.
As an alternative I could send you my saved file after finishing level 7, so you can start level 8 with the blade. Unfortunately this is not my original gameplay but one I did for testing, so I used cheat codes and you'll get a rank of Cheater. I suggest you use the other method (capture all enemy cities and heroes) instead.
But, you could use my saved game just to try out the artifact ;) As I said it's pretty cool.
Also, whatever you do, when you finish the campaign, you have to immediately start a new one and NOT go to the Main Menu and New Game. Otherwise, the final campaign will not be unlocked.
Basically, you finish the camapign you'll be to the campign selection screen with a check mark on the ones finished. You start a new one, save and then only can you close the game.
EDIT:
As a final resort, if beating the level becomes too tough, you could use cheat codes.