In many MMORPGs the number of players in one world is often limited to around a few thousand, but a notable example of the opposite is EVE Online, which accommodates several hundred thousand players on the same server, with over 60,000 playing simultaneously (June 2010[12]) at certain times. Some games allow characters to appear on any world, but not simultaneously (such as Seal Online: Evolution or Kolossium competition in Dofus); others limit each character to the world in which it was created. World of Warcraft has experimented with "cross-realm" (i.e. cross-server) interaction in player vs player "battlegrounds", using server clusters or "battlegroups" to co-ordinate players looking to participate in structured player vs player content such as the Warsong Gulch or Alterac Valley battlegrounds.[13] Additionally, patch 3.3, released on December 8, 2009, introduced a cross-realm "looking for group" system to help players form groups for instanced content (though not for open-world questing) from a larger pool of characters than their home server can necessarily provide.[14]