This one is relatively small but contains the last new bonus ship type of the expansion, a few important changes to Showdown Devices, and a few less-important-but-still-nice other changes.
That last bonus ship type is the "Neinzul Combat Carrier", which is a light combatant starship that can also build any youngling types you have unlocked. It also can always build a new unique type of youngling called the "Shrike", which is a fast cloaked raider-type ship sure to better enable humans everywhere to annoy the AI.
This is a standard update that you can download through the in-game updater itself, if you already have 4.000 or later. When you launch the game, you'll see the notice of the update having been found if you're connected to the Internet at the time. If you don't have 4.000 or later, you can download that here.