Posts from The griffin is immortal.

I can't seem to beat the second mission; there are no resources, all the stacks are weak, and I can't develop the Castle without resources. I just run back and forth, and it's not interesting at all. I played for a month, building only skeletons and peasants, and then I gave up and quit.

See the post above; I think I explained everything in detail. Let's just say the mission is challenging (for the hero) but not impossible...

I advise you to level up the Human Castle more because if Markel gets a decent upgrade, ideally right away with Fire Warriors, if that doesn't work out, then at least by level 2 in the mission.

Since both Castles are mainly resource gatherers, you won't hinder them. Markel won't be bothered until you enter the underground...

I explained how to quickly defeat the archers in the first week; you should experiment with griffins and the "Strike from the Sky" spell...

Markel, with his single vampire, can easily take the mine. Even with a weak build, a single vampire is still effective, although it's better to replay the first mission and use Fire Warriors; it will be much easier...

As for Fiona, machines are a must-have, as mentioned; the stacks are strong. I was lucky with the hut on Fiona's territory, and it gave me light, although there were still no mass casts...

I advise you to make a quick save and plan Fiona's build. Keep a notepad and write down the build. If you don't like it, restart until you have an optimal build. Once you have at least basic training halls, train 7 archers and then 20...
When Fiona reaches the maximum level, you can start the companion, who will stand at the portal from which the demons emerge, while Fiona goes further...
And one more thing, if you really try, Fiona and Markel can go to each other's territories. After defeating the first demon Castle, Fiona gets a portal to the city and can stand in a specific spot on the map and teleport to Mythgard. If Markel has a scholar, he can learn the spell and teleport to Claw, thereby boosting our main heroes, and thanks to this, the 3rd mission will seem like a walk in the park.

Good luck! If you really want to, you can even go to space; I'm not talking about the player, but I think someone who has completed the Master Campaign knows a thing or two.
Good luck!

I advise you to first make a quick save and outline Fiona's build, keep a notepad and write down the build; if you don't like it, restart until you have an optimal build...

The second mission is a real nightmare, and not just because of its difficulty. I couldn't complete it with my hero. I tried on Veteran difficulty. Victor arrived on the 4th day both times, and, by the way, the fire warriors didn't reach level 5 either. But that's just the beginning. I can't seem to finish the mission. The problem is this: I couldn't build the Angels for a long time because I couldn't gather enough troops to defend the mine; there were too few resources and money. Later, it wasn't critical to keep running back and forth to defend it (I should have been busy chasing down the demons), so I eventually gave up on that. When I built up a decent army and managed to take the garrison, I defeated the blue player. This probably backfired on me. While I skipped weeks, letting Markel gather his strength, I went to take the gem mine, and to my surprise, it turned out to be a quest-related mine and a very strong one. This quest appears in the main storyline, but since it's already completed, it can't be closed. The situation is this: Markel defeats Aiden, it seems, but he can't reach the garrison – the mission fails. Fiona can defeat the first Inferno Castle, but the path to the second is blocked. I even tried using a town portal to reach Markel and attack from there – the mission still fails (when Fiona approaches the garrison, but otherwise they communicate and exchange artifacts). I tried not touching the mine at all – the same dead end. Conclusion: the map is poorly designed; it doesn't account for perfectly legitimate player actions that make it impossible to complete. People have already written about Durgal – he's useless (they could have kept him in the dungeon and leveled him up, or given him a Tome of Darkness/Light, or at least a useful scroll), especially since he's freed at a late stage in the game. It would be good to display the tasks of the keymasters and farmers in the quest log – you don't always play continuously, and then it's hard to remember what they asked for. After Markel's dialogue with Aiden, it would be good to show him on the map (open him on the map) – they did meet, and also display Markel's decision in the quest log. It's difficult to build up an army for Markel – otherwise, it's impossible to defeat Aiden (although I didn't have the patience to reach the number of creatures shown in the screenshots above). Unfortunately, my playthrough ended here.

Added 22 minutes ago
And I'd like to elaborate on this part. Fiona starts the mission at level 1, with light, darkness, and a fallen knight.

I mean, we need to plan our build, and for that, we need the console...

the only thing I don't understand is whether Berserker and Subdue are blocked at all levels, or I'm just lucky

I started playing. No videos, no main quests, nothing. I can't build the Castle. What should I do?

Once again, regarding the demon castle in the second mission. There is a FLAG near the first castle; visit it, and it will unlock.
As for the choice, it's this: either you go to the church, which blocks the altar, or you go to the altar, which blocks the church. Accordingly, visiting the altar unlocks the vampires, and visiting the church unlocks the angels.

I started playing. No videos, no main quests, nothing. You can't build a castle. What should I do?