Journey

The map is certainly engaging; I managed to level up my hero significantly in the first month, capture a Castle where almost 5,000 dragons were stationed (it was a long battle). Then, I destroyed a lot of mummies and sent several heroes in different directions to clear the map. But I didn't have time to finish it.

Initially, my idea for the playthrough was quite simple: take Ornella, quickly level up her Mentoring skill, make other heroes high-level Necromancers, and constantly raise vampires. In addition, the "Spoils of War" skill allows you to have more than enough resources after capturing a Castle and defeating mummies to buy troops in all Castles and rebuild them.

You can see the hand of a master. It's a pity that it wasn't finished.
I also took Ornella (with bonuses), leveled her up to level 15 and mastered Summoning with Fire Warriors in the first four days (mainly raising different types of ghosts).
Summoned a ship, and on the 6th day, she defeated a horde of mummies across the river (about a million experience points), and also mentored two more Necromancers, so by the 8th day, there were over 700 units of Dark Energy.
And then it just took off.
I only went into the Underground to get the keys to the Armageddon Blade; I didn't capture any cities there.
I also took the "Spoils of War" skill for several auxiliary fighters, which helped me develop dynamically.
With the help of Sandro's Cloak and Subdue, I defeated the Necromancer garrison.
On the 26th or 27th day, I defeated 280,000 Black Dragons using the Secret Crystal, BPD (Battlefield Power-up Device), pairs of Ghosts, Fire Warriors, the Necromancer's Mark, and the game's AI features.
I captured the rebuilt Human and Orcish cities on the surface.
I gathered a lot of creatures from quests (mages, archer elves, dendroids, wyverns, etc.). I increased attack and defense skills (I almost maxed out all the upgrades on the main continent).
I took the Dwarven Repository, turned Logistics into full Light on the mentor, and corrected Darkness for all mass versions as well.
I gathered all available meat (the Temple of the Underworld is a great converter of living creatures into undead). I managed to gather about eight hundred vampires.
I defeated Biara.
Result - 42 days.
Sincerely, Simara.