The update adds co-op airship combat with any number of human and AI players to each side of the fight.
It also massively expands the features of the conquest mode:
A full-featured diplomacy system. The AI takes a "realpolitik" approach, and the system explains in detail why the AI likes or dislikes a diplomatic action. So no AI opponents that hate or love you for no clear reason. Your diplomatic actions also affect your reputation in the world as a whole.
I'm especially pleased with the ultimatum system, where you can send an interaction saying "do this or else I'll do this other thing". This can be "pay me tribute or I declare war" but also more out there things like "upgrade our non-aggression pact pact to a defensive pact or I'll cancel our trade treaty".
You can now upgrade your towns and cities with shipyards, factories, police stations, pleasure palaces, labs, and more. Balance your expenditures between building up your empire and conquering more of it.
There are new systems for logistics and city unrest, as well as a fully rewritten espionage system, a revamped technology tree, and a much prettier new map.
Finally, there are now special eras in conquest that change things up by having special rules. Like an Age of Piety that reduces unrest and gives the players a bunch of holy sites to fight over. Or an Age of Exploration that lets the players send out expeditions to find knowledge and valuables.
Airships: Conquer the Skies is a real-time strategy game where you build steampunk vehicles and fight with them against other players and weird monsters. It's been around for a number of years and is developed solo by David Stark.