Currently playing the mother of all HoMM 2 maps: the last map of the Wizard's Isle mini campaign from Price of Loyalty.
I seem to recall having to fight legions of Black Dragons at the end the first time I played it. I've seen people complaining about the map being impossible.
This map is interesting since you can use divide and conquer strategy.
In my game I was just about to invade the yellow player who is a coalition of every faction but necromancers. But the yellow player opened up all the barriers leading to red player's domain and powerful warlocks with large stacks of Black Dragons poured though. I only had like 5 Titans, and I had just wasted 14 K on buidling up my necro castle, so was short on cash.
So I decided to just bide my time with my army on a ship ready to land when it was safe. Red player defeated several of yellow's heroes, but eventually spread his forces to thin and Yellow beat him back, at which time my fleet, reinforced with more Titans, landed.
After dispatching of most of the remaining dangerous heroes and capturing a second Wizard castle with lots of Titans ready to be recruited, my barbarian hero with the Sphere of Negation (negates spell casting) headed for Red's domain. Red's remaining heroes and cities (except one each) were easily defeated, but the very last castle was defended by 100 Black Dragons, about 50 Green Dragons, and stacks of Hydra and Minataur Kings, which my current 15 Titans could not match, so having already beated the map before I called it quits.
The map is not really that difficult, since there is no chance of being invaded, but it takes lots of time and logistics to build up a big enough army to beat the final castle. In my game I also was very fortunate that my starting castle had Summon Boat in it's Magic Guild, which meant all my heroes could summon boat, and I was not depedent on the Summon Boat scroll that could be found on a small island.