In a snapshot, here's what's new for the Vasari.
A. Orkulus (Orky) Starbase: Probably the biggest addition, its notable for several reasons. First and formost it's the only starbase that can move around its gravity well, allowing it to chase antistructure ships or carriers that are the most popular methods of killing starbases outside of their range. It also has the highest DPS of any starbase, and it has several other upgrades that help it engage fleets and even other starbases. It's also unlocked a teir earlier than the other races starbases, and this combined with the assault deployment tech allow it to be used offensively by building it quickly in other players gravity wells, thus the so called Starbase rush. Also its unique in that it is deployed from the Vasari colony frigate instead of a dedicated starbase constructor.
B. Sivuskras Ruiner (minelayer): Mines were another new feature in Entrenchment, and each faction had their own way of deploying them. The TEC just built them with planet constructors, the Advent deploys them from Hangar defense structures or carrier cruisers, and the Vasari get their own dedicated minelayer ship, the Sivuskras Ruiner. As a mobile layer, it can be used to deploy mines anywhere, even in gravity wells you don't own (unlike the TEC). Also, the Vasari get access to to type of mines, conventional exposive mines or "gravity mines", which slow down the enemy rather than damage them (though these are considered far less effective).
C. Other Defensive Research - The new expansion also features additions to the standard static defense platforms. With research, the Vasari missile platform can prevent targeted ships from "passive regeneration", the natural regeneration of hull, shield and antimatter points, for some time. This is particularly devestating to capitalships, especially if you've got a starbase or fleet that is capable of destroying the said capitalship. The Hanger defense platform also gets an ability to "phase trap" enemy strikecraft, essentially leaving them immobile and unable to fire, but invinsible at the same time, which allows you some time to go after the carriers unmolested, or at least reduce the incoming damage from strikecraft.
(?) D. Kostura Cannon - This might have been added to regular Sins already, but the Kostura Cannon "superweapon" gains the additional effect of creating a phase stabilizer node at whatever planet the cannon is fired at. This basically allows you to conduct surprise attacks, as you can just jump your fleet from any planet with a phase gate and directly jump to the enemies homeworld or any other planet of interest, completely bypassing any planets (and their defenders) in between. However, it doesn't last forever, so you may not have an escape route unless you bring a level 6 marauder with you.
Any many other smaller that will undoubtably be in the change logs Annatar linked too.
