So I left the site fora short time right after the arena was announced, so I never got to figure out where/what it was. does anyone have a link to something that could fill me in?

It's in Ethernia, which you can reach after beating Umbra Forest.

It's essentially a place to challenge opponents with special attacks and patterns. They're different from traditional battles and requite strategy and well equipped pets.

There's a lvl25 and lvl50 bracket. You can only get to lvl50 bracket when you clear all of lvl25.
You can use any pet from lvl0-lvl25 for the first bracket, but it's recommended to have lvl25 pets with good equips.
For lvl50, it's recommended lvl50 pets.

There's a subforum called Arena Discussion that has threads discussing how to fight the monsters in the arena.

Ah thanks somehow I completely missed that forum ><