The castle of your dreams.

I would remove the Conflux and add its units as neutral creatures. I would also add a Castle of Assassins with the "Veil of Darkness" ability, affecting many squares, and the ability to transform castles, like in Inferno. As for the units, there could be thieves, snipers, boars, and dart throwers, for example, from levels 6 and 7, along with dark elves and Anubis. As for special features:

Added 35 seconds later
and diplomacy for everyone.