Soon we would have wipe so PvP was turned on! Now it’s possible to perform a hostile action toward other player and it would trigger hostility for both players (example of hostile action: to throw something at another player). Also you cound turn on hostile through ‘party’ screen.
UPDATE: Hostility is ‘on’ by default, no need to turn on PvP manually 😀
Please do not attack low lvl characters if you got high lvl 😛
It’s temporary event, till server would be updated. Have fun!