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I like the Heroes in the Castle... Adel, of course (although I never use her for aesthetic reasons), the hero with the Prayer skill is very good, and Orrin with his ranged attack, which plays a significant role when you have 2 ranged units in your army...
and also - please remember that with random map generation, the spawn points play a big role, and humans have a richer selection than most other factions, and the terrain is good - it's a civilization, after all! (....I don't like swamps though))
The downsides, of course, are the limitations in magic, first of all... the risk of being left without Dimension Door, Fly, and Town Portal for some is quite high.... and Fanatics are weak for level 5 (which, in my opinion, should be one of the main units), although they do shoot.
In general, if you look at the Castle, it's through the lens of comparison with other factions...
The situation with the Rampart is as follows (I'm mainly considering the upgraded versions):
Centaurs - Halberdiers. Almost comparable units, but Centaurs are slightly faster and don't require stone to build... although they are more expensive.
Gnomes - Archers. Well, Archers are certainly more useful, especially at the beginning. There are more Gnomes in terms of growth rate, they are more resilient, and their task is to support and take the brunt of the attack (and withstand it!!)... Archers are good at the beginning, then they become a nuisance for the enemy (annoying, but no more), Gnomes, on the contrary, have magic resistance...
Elves - Griffins. Great Elves, despite having very little health, are a powerful unit with a double attack (don't forget that 2 attacks increase the chance of Luck triggering, which the Rampart almost always has in its "offerings"). Griffins, with a comparable growth rate to Elves, don't shoot... and importantly, Elves can finish a battle with a strong opponent without losses (especially if their movement speed is increased with the Ivory Tower), while Griffins cannot, as they fight in melee and losses are quite possible, although small (still, it's a strong unit - I'm not arguing).
Pegasus - Crusaders. Hmm. Well, what can I say.... I like the Rampart... but not enough to lie to its face-)))))). Crusaders are stronger. Significantly. Proven=)))
Dryads - Fanatics. But here it's interesting: completely different roles, as in the case of Gnomes, but in reverse. Fanatics need to be protected from melee combat, while Dryads can protect any unit themselves. Here, I am completely on the side of Dryads - their ease of construction (in the first week with 200% difficulty), a growth rate of 8 per week, and the ability to hold their ground really appeal to me (although it's not rational to use them against Fanatics and they move slowly). In addition, Tactics is a frequent skill for Rampart Rangers, and in a serious battle, you can position them well so that the enemy cannot flank them.
Unicorns - Champions. Difficult to compare. On the one hand, Unicorns can blind, which is cool, and they provide magic resistance, which is also good. On the other hand, the cavalry charge deals significant damage. And they are built only with wood and gold and without any prerequisites for building levels 5 and 6. I think the units are comparable, with a slight advantage for Champions.
Gold Dragons - Archangels. Dragons are immune to the magic of the Castle, as Town Portal is not available in the Castle. But in direct combat, Archangels are stronger (although not significantly). Dragons are difficult to build, but they only require crystals. I don't think that in approximately the same spawn conditions, Angels will appear much earlier than Dragons.
This is just my opinion, if there are any gross errors - please forgive me and don't judge too harshly-))))))!!