All castles in Heroes 3.

I play at 160%, and many play at this difficulty level.

In the first week, it's unlikely you'll be able to deploy Devils, even at 100%, at least that's how it seems to me.

For me, the main task for leveling up is to defend against the first Pandora's Box. Either there will be money to hire an army, or there will be an army, or there will be an army (it depends on luck, whether it will be strong enough for the second week or not), or there will be useful spells. I somehow rely on gaining experience; skills appear, and it becomes easier. If the Pandora's Box is guarded by 20-49 Griffins, Mummies, or other medium-level neutrals, then it's great; if not, then you need stronger troops.

My task is to quickly defeat the opponent because if you delay, Inferno isn't particularly strong. What does Inferno have? Ifrits might not be defeated; there will be too many of them, but it's worse with Devils. In the 3rd or 4th month, they will be defeated by Red Dragons or Titans. I usually build a Capitol either at the end of the second week if I have enough gold or after capturing the second Castle; usually, the computer already has a generator producing 2,000 resources. In total, that's an increase of 4,000 (my Castle + the computer's Castle).
[br][/br]I usually can't deploy Devils in the 3rd week due to a lack of Mercury. On the "L" difficulty level, without a Dungeon, there definitely isn't enough, especially when 8 people are playing. So, I have to save up Mercury and mostly avoid upgrading 2nd-tier Golems and Pit Lords with Gogs. Although I also don't usually upgrade Gogs because they often attack my own units.