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There is a very easy way to complete this scenario (Hero difficulty).
First, at the start, sail to Tilshek, collecting resources along the way. Ideally, you should find an artifact that grants knowledge or attack (for the ballista). The first battle is the most difficult on the map; if you are lucky with the battlefield and other factors, the losses will be minimal.
Tilshek takes the entire army except for the centaurs; you can also leave the sextant with the main hero. Tilshek sails directly to take the castle, while the main hero sails a little further to the island with the prison, picks up the artifact, and then sails to join Tilshek. The main hero needs the centaurs to prevent the mage heroes from attacking the defenseless Kunyak; with the centaurs, you will definitely reach him without any problems.
Meanwhile, Tilshek clears everything without losses, not picking up the defeated enemies, except for the lighthouse.
Clear the island, build up money and an army in the city. Only take wood for leveling up after you have leveled up in battles. It would be good to get Fire Arrows. Mighty Shout is also a good skill.
Before venturing into the ocean with Tilshek, you need to buy him a talisman that summons a boat; in this scenario, stealing boats from the computer can create many problems for you.
After getting the talisman, the army, and all the artifacts, Tilshek clears the island with the gold mine, then sails to the first city of mages and clears everything he sees there (the ring that gives +2 HP is especially important).
If you play skillfully, without losing troops and continuously building up, by the time Tilshek clears everything except the island with the sulfur mine and the island with the second city of mages, you will have an army in the castle that will make capturing the first city of mages one of the easiest battles in the scenario.
In the castle, it is important to learn all the shouts; if you get a Fear or Horde Fury shout right away, that's great, but even without them, nothing is difficult. The castle is taken with small losses. For the army, the most important things are the goblin's magic weakening, the warmonger, and a free cyclops (you can replace this with the "catapult" perk), a leader for initiative, and the rest depending on your wishes/capabilities.
At this point, it is very likely that Lorenzo, with his overwhelming army, will suddenly appear and you won't be able to escape from him. It is unknown how to avoid this exactly, but there is a way: save more often (manually), do not clear the island with the sulfur mine and the second island of mages before taking the first city of mages, but sometimes he doesn't react to anything.
The orange mages will "harass" the map quite annoyingly, but with good logistics, it will be easy to catch them by sea; there won't be any super-strong ones there, so the main hero will also be able to defend himself in his own castle if you happen to miss someone.
As soon as we get the second city of the orcs, we start actively building it up, preferably with 5 first-tier buildings with upgrades (if the economy is failing, you can transport them to the first city or fort for upgrades). The problem with gold can be solved by freely joining neutral creatures, if any appear, by selling them on the slave market (I got 66 earth elementals, which were sold for 30k gold).
Put a level 6 creature on the astrologer. A week of artifacts, gold, life, and alliance is everything we need. A week of artifacts is one of the most profitable.
And finally: 1k goblins, 500-600 centaurs, 500-600 warmongers, under 200 shamans and executioners (there can be much fewer shamans), 15-20 wyverns (meat) and cyclops (you still need to replace the free ones with bloodthirsty ones for the finale). The hero is level 28. The second city of mages is taken without problems, and we open the passage to the red city. Either it will sail to us itself, or you will catch up with it. Don't fight on ships or in the castle. Lorenzo is defeated in an open field, but it is important to understand that after this, you will need to leave a strike force to take Castle Gate.
In the battle with Lorenzo, it is important to survive the first attacks of the horses, angels, and griffins. Then, Tilshek continuously casts +400 Fury on the warmonger, and it, receiving negligible damage, destroys everything, receiving infinite retaliation at the second level of Fury. Ideally, you should keep it for taking the castle. Frightening Shout can play a key role in this battle.
In the castle, there is a level 1 hero; after opening the gates, the red hero signs his own death warrant.
Four and a half months will be more than enough, considering that we spent the first week and a half sailing with Tilshek.
I hope this will be useful to someone =)