The stats of creatures are currently being tested. If you mean additional creature properties depending on their experience level, this issue has not yet been finally resolved. I hope we will decide on this in the near future.

A special creature, as I understand it, is a commander. I wrote about them above.
The Castle will be focused on crystals.
The Midshipman's priority skills will be Morale, Tactics, Ballistics, and Attack. In general, Midshipmen are an attacking unit for the city, developed for a rush strategy.
Harbor Mages – Enchanters – are a priority for a defense strategy, with long and powerful magical development, mainly in the Water and Air magic schools (+ unique water spells).
There will be no hero whose specialty is Sea Serpents.
A composite artifact will most likely not be included. Although the question of artifacts remains open.
Since the Harbor is positioned as having a neutral alignment, there will be no special hatred towards any races.