Which castle is the most difficult?

In other words, if Craig Heg comes to you with Roars at the beginning of the second week, can your mage easily defeat him?

Well, if he doesn't have any tactics or haste, but only Roars. Then what's so special about that? You can solve it with one lightning bolt. With some Grindan. And if you also sit in a town, there are no options. Of course, if he brings another ten angels, then that's the end.

I thought that on a small map, speed and warrior skills are more important than a level 2 magic guild and 30 mana... But you know better.

30 mana for a hero starting from a Conflux of level 1. That's ridiculous. Or take heroes from the Dungeon: 2 knowledge + doubling already gives 40. Without leveling them up.
And if you level them up to level 7, and find some artifact for strength or knowledge, then it looks completely different. Definitely not 30.

At level thirty, the difference isn't that big, plus artifacts still exist.

Okay, do an experiment. Take Tazara at level 25, and take some mage, whichever you like best. Give them both the same amount of experience in the editor. See how they leveled up. On primary stats. "Not such a big difference"?))
You can also give them the same army and magic and try to have a battle. And then, for the second time, equip them with a red orb. And fight again and see what happens.

Well, as far as I know, a warrior with wisdom, earth, air, water, intelligence is rare. Or am I forgetting something...

Water and intelligence are superfluous. Earth or air is enough.
Wisdom is no problem; it's offered every 6th and 12th level.
And if you get lucky with this log, attack, defense, tactics - it's a fairy tale.

But tell me, can a warrior cast Berserk on five enemy units?

If there's expert fire, why not?
Of course, fire magic itself isn't popular, but that's just details.

clone archers, read prayers to everyone,

it's all the same.

see where the enemy heroes are, teleport to any town, etc., in one game. I won't talk about the difference in mana...

It's more important to find the ability to deal damage, fly, teleport, etc. And then you will find how to use them. As a rule, the main hero knows earth magic. So there will be no problems with the city. You can even use flight without air. And such a cheat artifact as wings doesn't hurt either.

Earlier you wrote that lizards were definitely better...

I didn't write "definitely." I said:

play as Vistan. And see how "weak" they are.

Of course, it depends on what parameters the opponent's hero has, the number of best archers, and generally the army he has. Of course, magic cannot be ignored. It is quite possible to win against Valesk with Vistan. And against neutrals, he just shines.

Thank you for opening my eyes to warriors.

Your eyes would open much wider if you found the time and started playing online))

Well, honestly, I rarely play Heroes (because I have very little free time) and yes, against the AI, but I always play on the Queen difficulty and interesting, complex maps (campaigns) from users... I won't argue anymore; I've already spent today's annual limit on the forum:)

Playing against the Artificial Idiot is funny in itself, but it's not an indicator. Yes, sometimes it's fun. But building strategies based on this is useless. They will only work against the AI, and against a human player, it will be a failure.

And as a teaser, here's the final table of the "Favorites in Battle 3" tournament (everyone registers by choosing their favorite city and plays with it)
40 participants
/attachments/35765/
winner: Swamp

Favorites in Battle 4 - 78 participants
/attachments/35766/
winner: Castle, Swamp in 5th place.
How did that happen? The Swamp should have been at the bottom))

and here's some old statistics for winter 2009, results of the season from 470 games, 86 players
/attachments/12006/

The strongest cities were Rampart, Swamp, Dungeon, Stronghold, Necropolis (% difference is minimal). At the same time, Castle shared 6th place with Conflux, and Tower and Inferno lived up to expectations.

Added after 20 minutes

But isn't the conversation about mastering castles? It's still a long way before you start learning how to keep pace.

What do you mean by "mastering"? Building a Capitol?
Of course, anyone can build it. But actually playing, which naturally implies keeping pace and everything else - is easier with one city than with another. That's what we're talking about.