I was able to play the Advent yesterday on my game after a decently sized download but I'm unable to pick them today (after a midnight small update to my game that occured while I was playing and made it crash). I was taking my time and just testing Advent out, especially the titan. Most of its abilities were unimpressive but it does have an instant acquire planet feature. That was pretty cool. Just get close tot he planet and "the will of the Unity will bring the planet under your control".
The other features I remember were, one where it would draw on up 50 friendly ships in a small area and then channel their rage into a beam weapon that would do some decent damage to enemy structures every 20 seconds or so. Only effective against structures, starbases and titans.
The other abilities where the usual heath boast, damage boast like the TEC and a stat nerfing ability around the titan ship, reduced enemy speed by like 30% and damage by 25%.
The last one was something about taking over control of enemy ships not effective on starbases, titans or structures.
The firepower of the Advent titan seemed unimpressive, I was pretty much at a dead lock with a starbase until I introduced a capital ship to tilt the odds in my favor.
The culture bonuses seemed to be missing but I expect that's because it was beta.
There was a new capital ship that was fat on one end and skinny on the other...its abilities were pointless....when it died I didn't care.
Edit: I remembered another ability of the advent Titan, it can increase its antimatter stats.