A new player checking out these forums may see AO veterans using the terms RK19 and RK5 to reference the two existing servers. Obviously RK19 refers to the server labeled Rubi-Ka 2019, but why do we call Rubi-Ka RK5? The answer is found in the history of Anarchy Online.
RK1 - The Atlantean Server. One of two original* servers for Anarchy Online, many considered this to be the “main” server due to its higher population and noticeably more active rp and social community. This server also had a huge froob population since almost everyone was rolling their first character on RK1.
RK2 - The Rimor Server. The other original* server for anarchy Online from way back in the day. While this server had a noticeably lower population, many players would roll on this server just to make pvp twinks with the extra character slots, so this server had a very active pvp community.
*Rimor may or may not have launched shortly after Atlantean (Can’t confirm)
RK3 - Die Neue Welt (The New World) Server. The German speaking server for Anarchy Online, launched in 2003. This server always had a fraction of the population compared to RK1 or RK2. This was the first server to Merge into the other existing servers at the time (RK1 and RK2). From its launch 2003 to its closing in November 2010, AO had three concurrent servers.
RK4 - The Real World. IRL. This is just how addicted AO players refer to life while not in Rubi-Ka. “Hold on, I’m catching RK4 aggro.” This caught on some time after the release of Shadowlands.
RK5 - Post-Merge Rubi-Ka. This is the culmination of RK1, 2, and 3. In February 2013, Funcom rolled out patch 18.6, a drastic turning point for the game. While merging RK1 and RK2, It also ended froob organizations and outdoor player owned cities. In the previous patch 18.5, The GMS was revamped from the old system (with player shops located on outdoor organization city plots) into the GMI as we know it today. These drastic changes reshaped the way the game was played. This patch was also the Docaholic ring patch, and the patch which disabled /pet hunt and auto-retaliate. For the next six years, AO would have only one server, RK5.
RK19 - The temporary progression server for Anarchy Online launched in 2019. Paid only, pretty cool I guess, it was really fun in the first few weeks, I honestly cant comment because I don’t play this server any more.