South Korea's G-Star event is over and here is what we learned.

PVP

PvP is important to the TERA developers and they have worked diligently to provide robust methods of “slaying thine enemy”. The basic form of PvP will be a duel, which would take place between two consenting players anywhere at any time.  Deathmatches, aka free-for-alls, will be group matches that award glory and honor to the victors (and possibly the not-quite victors, but definitely not the losers). 

Battlegrounds, or large-scale group matches, will be implemented. However, until more stress testing is done it is difficult to determine the size of these matches. Battles of 5v5 up to 15v15 have been considered, but in a game as action-oriented and non-target based as TERA, latency and computer performance play a bigger role than ever in balance. There was also mention of commanding officers performing in these battles to direct troops and influence other aspects of the battle. 

And last, but certainly not least, it was promised that full open PvP servers will be available for those of us who love crush everyone in our path and leave wakes of destruction.

Guilds

The function and abilities of guilds were touched upon as well at G-Star. You can expect to see standard abilities like chatting, joining and quitting commands, guild titles or ranks, and likely more of these common abilities within guilds. One of the biggest bonuses to being part of a guild in TERA is the help they can provide when you find yourself running for an elected office (see the next section for political system information).  The backing of a powerful guild and their votes is likely to become priceless, if not absolutely necessary, to be elected to office. 

Guildmasters will also be allowed to bestow specific titles to certain members, however exactly how these titles display to the public or other guild members is still under discussion. Guilds will also be able to purchase in-game instanced housing out of one of the three main cities. The bigger, wealthier, and more politically powerful guilds will, of course, have the biggest estates.

Finally, members will gain an ability that will allow them to return to their guild hall from anywhere in the world. This is probably reason enough to join a guild as time spent traveling is time not spent killing, crafting, or otherwise getting your adventure fix.