The title of the topic is just as important as the content....
The best monster doesn't necessarily mean the strongest!!!

The poll showed that Nagas are not the best monsters - although they might win in a one-on-one fight...

But most often, all situations are considered... and the Dark Knight has many properties:
double damage
curse
immunity to magic affecting the mind
lack of morality
and in terms of parameters - he will be slightly inferior to the Naga in damage - but superior in speed!!!
All these advantages are more attractive than "retaliation" (which, by the way, is not difficult to achieve in battle)

And regarding taking a Castle (you say it's neutral :smile26: )
There are very few cases (almost none) where a neutral Castle with a moat is also defended by archers :)