So, there I am, about to try and bring Kraeger (or however you type his name) to Imperial (in)justice.

I take the necromancer town, build it up, take the saw mill in the south, and (not wanting to go too far north), only took the gold mine just north of the land bridge in my last attempt.

Every frickin' time, even if I don't go cross that bridge at all, I soon get raided by an enemy hero with army so powerful there is just no bloody way I'm able to beat him.

Is there some way I don't know to beat this map, or should I just start again, over and over, until the RNG or whatever favors me, and the enemy keeps to himself for a while? Because frankly, if it's the latter case, I might as well cheat, get myself some black dragons, and move past this crappy map.

Did you get the Elven Alliance bonus?

Been really long time since I played, so I don't remember the details. The last levels could be tought, but I don't recall having all that much trouble with the alliances bonus.

Yeah, I did. I don't remember any elven stacks in the areas that I explored, though (but as mentioned, I didn't go very far north).

I just looked and my saves from that time are long gone, so I can't offer you help :( I do remember the prize from this campaign being useful.

This walkthrough suggests:
https://www.gamefaqs.com/pc/197549-heroes-of-might-and-magic-ii-the-price-of-loyalty/faqs/12762
"DONT EXPLORE TOO FAR AWAY! If a Red or Blue enemy hero spots you, they will rush your castle, ending the scenario very quickly. Try to attack weaker stacks, as they build up your Skeleton stack when you defeat them. Try to capture any nearby mines, and remember to not travel too far."

This one:
https://www.gamefaqs.com/pc/932491-heroes-of-might-and-magic-ii-gold/faqs/2044
"I strongly suggest winning this scenario before tackling the last one (POL 8) for reasons that will be made clear in the conclusion... Contrary to most of my other add-on strategies, this one was written from my 3rd try at the map. Why you may ask ? Simply because I got killed twice in the first month of play by a super-strong enemy hero (one time red, the other time blue) who headed straight for my castle while it was still too weak.
...
9) There's a nearby gold mine to the north of your castle... Ignore the southern sawmill and cross the bridge.
10) Attack every possible wandering stack in order to increase your number of skeletons. Do not attack stacks that are too powerful... Use your instincts.
11) Capture all mines in the clearing south of the swamp.
12) Explore the swamp but watch out for enemy heroes. You're not strong enough to encounter them yet.
13) Do not go beyond the Observation Tower but do take the free grand elves on the western border of the swamp.
14) IMPORTANT : You do not want the enemy (blue or red) to notice your exploring necromancer. If one does "detect" you, he will probably rush and conquer your castle. Therefore stay far away from any opposing color until you are ready for the offensive."

Both warn of these heroes, and both suggest you don't explore too much. Check both links if you want for further details.

Sorry I can't help you more :(
You might have to restart it once. What I do remember is that I finished all the levels in all the campaigns on my first try, except the final level of POL due to a glitch. So I don't think you'll have to restart it several times. Make multiple saves, so you can go back a little bit further if you draw the attention of any of the strong heroes.

I did in fact restart a bunch of times, with the enemy heroes coming to me even if I did nothing to get their attention (as in, I was staying south of the "bridge"), that's why I was so frustrated with it (as the map seems to rely on the randomness factor, will they come for me unprovoked, or will they not?), bu after another reload they didn't for a change, giving me enough time to build up, and it seems to be going okay so far.

I think it's still a crappy level, though, unless I'm just missing something and it isn't as random as it seems to be.

I saw those walkthroughs you're quoting too (at least the first one, not sure about the second), but they weren't helping what seems to be the problem to me.

Thanks for the help anyhow. :)

Glad it's going well. Good luck.

Looks like I was just lucky they didn't go after me on my first attempt. If it's indeed random, then crappy level design. It could be non-random, but a combination of factors that's causing the AI to behave the way he does, but if it appears random to the player and he has to guess at what it is he's doing that's triggering the enemy, it's still crappy level design.

Guys.
This map is quite simple. You just need to:
1. Rush grabbing the first town and upgrade it to get the +1000 gold per day. Then immediately recruit a second hero to do pick up duty. But first, both heroes should rush north to collect 2 or 3 stacks of elves. Sometimes you are lucky and a stack of elves guard the alchemist lab northeast of the necromancer town. This gives u 15-20 elves if so. Further north, at the very west part of the map, there are 2 stacks of elves or grand elves totalling about 40. Using these stacks you have 40-60 elves + your starting necromancer units. Use these to RUSH THE FIRST KNIGHT. This knight is quite adventurous so he will usually leave his castle open. Capture his castle while his main hero is off gallavanting. He will turn around immediately when you take his castle. By then the castle usually has 1-2 arrow towers, a moat and sometimes even fortifications, making his melee units (whom are numerous) substantially weaker. Use your powerful magic (helmet of anduran) + lightning bolt or cold ray to kill his huge stack of rangers (50-100) or just blind them whilst using your elves on the rest of his army. Save the vampires SPECIFICALLY so they can attack the rangers if the rangers are unsupported by melee units so they cannot use their powerful ranged attack.

Doing this will usually kill the blue Knight early on, giving you 2 castles, numerous mines and a lot of remaining pickups for your second and third hero to grab. You also have 2 gold mines.

Do NOT spend any money except for a market place in the necromancer castle. You should focus on getting the Knight castles and their units as there are about 10 knight castles in the map. If you are lucky, you will be able to recruit the enemy heroes you defeat. They are level 9-13, and you can transfer your artifacts to them (don't forget to visit the Xanadu north with your main hero, whichever you choose).

This is NOT a map where you're supposed to slowly build up your necromancer fort. You are supposed to capture the knights early on, even their defeated heroes, and use this against the other knights. Use magic and defenders advantage to capture 1 castle at a time. Once you've taken most of Green's castles the map is all but won. Kreager himself has about 20 crusaders, 40 champs, 100 rangers, 50 grand swordsmen and 60 veteran pikemen. With 7-8 castles churning out units you will have more in 2 weeks of new dwellings. Then just go kill him. He usually has patehetically bad spells and spell power. There are multiple ways to weaken him if you come in with an inferior army as well. Like sending 3-4 fodder heroes to absorb his spell points before engaging him with your main army, and just abusing blind on his paladins and rangers and defeat the rest in detail.

The TRUE challenge is map 8, if red player gets dimension door. If so, GOOD LUCK. You're up against 500 power liches, 40 black dragons and 40 bone dragons by month 3.