Having a guild is important in Revelation Online. Then again, having a guild is important in a lot of games, so Revelation Online has to do some extra work to make guilds into big, distinct entities. For example, by giving guilds their own guild islands, potential control of major cities, lots of assets, and a whole system of Guild Quests for members to take part in. Once you hit level 25, you can drop money and assemble your co-conspirators and start creating the guild you want.
Guild members can contribute to the guild through the aforementioned Guild Quests or just by donating money and items to the guild; meanwhile, officers can help coordinate the guild, hire NPCs to work on the guild island, construct buildings, and so forth. Check out the trailer just below for a look at what the guild system in the game offers players; as you have probably gathered, it's pretty extensive.