This one is out tonight instead of Monday because a recent change broke the tutorial.
But it also contains two significant bits of content for the Ancient Shadows expansion: a variant of the Clusters map type with more outlandish intra-cluster arrangement, and a new minor faction: the Dark Spire.
Some of you may be thinking "Hey, I've already run into the Dark Spire in a nebula!". Well, you're right, and there's a degree of overlap here. But this is actually a Minor Faction that can be enabled in the lobby, and doesn't have anything to do with the nebula scenarios or champions. It can be pretty intense, though the balance numbers are only based on preliminary testing and may need substantial adjustment.
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.