I just had a huge battle against  a Vasari fleet. I had an Advent fleet.  I had a bunch of about 40 heavy cruisers that at one point I could not make turn or move or fire on the enemy.  They hung in space and got massacred (as did about 40% of all my ships).  What hit my fleet?  I looked in the manual to try to figure out what ships or weapons the Vasari used but couldnt firgure it out.