Arena combat is a staple of most MMORPGs, and Ashes of Creation is no different. Ashes is going to be using a traditional Arena System, and arena combat will be the only known time where PvP combat is taking place in an instance instead of in the open world. The current plan is to offer 1vs1, 3vs3, 5vs5 matches, as well as the possibility of having a 20 person FFA (free-for-all) Deathmatch. It is possible the arena system may allow for matches cross-server; however, nothing on that is certain or finalized. Additionally, while there is no guild vs guild option in the Arenas, players are free to make pre-made groups before queuing.
Since Intrepid is not balancing Ashes of Creation for 1vs1 gameplay, several people have questioned why there is a 1v1 arena, given the possibility and probability that you will encounter your hard counters while doing Arenas. The answer to this is practice. Match-ups of 1v1 allows players to encounter a wide range of opponents so they can see what works best about their class and what their inherent weaknesses are.
There will be tangible rewards from Arena Grinding, however, gearing up through the arenas system is not currently on the roadmap. The rewards for arena performance will be cosmetics, titles, and possibly perks from the PvP season system that has been mentioned. There will also be bragging rights through the arena ladder system which displays your performance history.