The Vasari, instead of getting their own cruiser, use the Jarun Migrator for their construction of Orkulus Star Bases. The Advent get the Talion Savior as their Construction Cruiser, which becomes the Transcencia Star Base. The TEC get the Raloz Heavy Constructor for their Construction Cruiser, which becomes the Argonev Star Base. There can only be one Star Base per gravity well per player, though stars can have four. A Star Base allows one to further strengthen their current gravity wells, or colonize a previously un-colonizable gravity well (allowing you to build even longer trading routes).

The Star Base is built with a Star Base Construction Cruiser, researched in each race's Defense Tree. The Advent's Defense Tree is the Security Tree, and the Vasari rely on the Fortification Tree to bolster their defenses. The TEC use the imaginatively-named Defense Tree for their upgrades. The Defense Tree also contains the Star Base upgrades as well as the upgrades for tactical structures. In addition, each race can now get mines. The Defense Research Trees are now where you get upgrades for hangars, defense platforms, etc. As well as the main feature being the star base. This expansion includes many improvements to current defenses and completely new ones. The races have come to a stalemate and are fortifying their territories to prepare themselves for the long run.

Sins of a solar empire v1.9 trainer