In the first mission of the Campaigns, there is no mentor before the transition to the dwarves, but there is one later.
In the second mission of the Campaigns, the main character's mentor is free, and the demons have a guard of a 7th-level creature with a hellish bonus, which can be quite difficult to overcome.
In the third mission, there are 20-30 dark elf bonuses in the garrison.
In the 4th mission, there is a mountain of undead.
In the 5th mission, the guard doesn't seem to be very strong.
Added 13 hours 56 minutes ago
Well, I have to replay the 4th mission :( http://c2n.me/400HCyk and right next to it, an elf ran past a blue garrison into the darkness.
It seems that everything went well at the beginning, the neutrals started to break through, I needed to take both the tent and the machine - I took the tent, but the nasty level didn't offer the machine later... A month passed, and I reached level 19, and all I managed to upgrade were demonic skills, and here is this https://c2n.me/400HGOR. The artifacts are bad - a ring of elements, a trident, a lion's collar, a portal scroll (requires 100 mana, but I have a maximum of 60) and a small bag of gold. 14 down horses, 150 demons, and 6 improved imps (before the battle with the elves for the mine, there were 150, but this doesn't change anything). I couldn't get the necromancer's cloak from the dead horseman because a stupid, uncontrollable ballista was shooting at 3 knights, who were blocking the passage for the others, and the spells didn't do much, and there is no witchcraft. I think they will quickly pass through the garrison of 5/10/25/85/250/500/550. It's a pity, it was a good start, but due to the random level, which offered bad things, I will have to replay it + some good artifacts, like the cloak, were not collected. The Castle won't save me. I can't even break through the neutral army in this composition, let alone a strong mage :(
Well, the garrison helped a little, but it's not much :) http://c2n.me/400IqWM
I started again - https://c2n.me/400NhKF it's better :) you can level up (and the artifacts are better).
2nd month, level 23 https://c2n.me/400RctQ, https://c2n.me/400RdHA it's better, if the leveling doesn't work, it's better to replay it)
http://c2n.me/400YUe9