There is likely to be one or more member ranks
Guild-master: This rank is created by aion gold default and must exist. You can rename it to something else but it is always the top rank. It can only ever have 1 member. And it has all the privileges by default. This rank is the defacto “in charge” person. Even if your guild is run by committee, the GM ranked person can demote and remove any other member in the guild.
Officer: Regardless of what you call the rank or ranks, most guilds will have at least one officer rank. Typically they can do things like add new members, remove members, set the message of the day and things like that. You may have as few or as many officers as you wish. By default, one officer rank is setup with basic officer powers granted to it.
Member: There is likely to be one or more member ranks in the guild. By default the ranks of Veteran and Member are setup. They are essential the same with the names of the ranks showing a hierarchy of who is “higher” in the guild. Who gets assigned to what rank is up to you. Typically the member ranks have a lot less power granted to them and often simply can talk in guild-say and read guild-say.
