Recently a ffa PvP arena has been added to the PvE servers. This area costs 10 platinum faction coins to gain entry.
If you decide to go check this area out, be aware that if you are killed the other player gets a percentage of any money that you carry. It's a very good practice to visit the bank and deposit all but enough money to rift with. They do not make this very clear when you enter, so be warned!
When you get a kill in the arena, you gain "Infamy". You can spend infamy on chests that offer rewards, but to open these chests you need a key that drops from an NPC that spawns inside the arena and takes a good 10-15 minutes to kill. Once you attack this mob nobody else can assist you, heal you, buff you, etc. It's strictly a solo fight. While you are killing this mob you are not locked out in any way from PvP so anyone can come kill you. I've found it's best to either A) have a full group to defend you or B) go late at night when nobody is in the arena to get the key.
Overall, my impression of this arena is one of poor design, and the rewards are pretty pathetic from what I've seen so far. (And you lose the key once you open a chest so you have to do the NPC fight again) Still, if you're stuck on the PvE server and want to go test your mettle, this is a place to do it! It can be fun - though remember that at anytime you can find yourself being attacked by a full raid force as teaming inside the arena - including up to 24 man raid forces - is allowed. The only rule inside the arena is: There are no rules! If you're a serious PvP'er though I'd recommend sticking with Sartok.