RA = Returnng Armada.  It's a Level 8 Vasari ability.  Before version 1.1 it was extremely powerful but was nerfed for v1.1.  Vasari players would build phase stabilizers and conduct some civilian research and then free (!!!) ships would start to appear at gravity wells that contained the phase stabilizers.  If you could put up 15-20 stabilizers then you could quickly mass a 2300 fleet supply-sized fleet and squash the other players.  However, it was only really feasible to make the huge investment needed to get it up and running on large and huge maps (especially multistars).  It was the sort of thing where a Vasari player could publicly announce, "I have attained Returning Armada, the game is over."  RA was not invincible and there were ways of addressing and taking it down, but your team would need to have the upper hand already to really do it (or someone else on the team who had RA running himself).

Today as of version 1.1 you have to pay credits and resources to activate it.  It's still a good deal but it isn't nearly as overpowered as it used to be.