Guilds can have from 1 to 50 players. Being in the same guild does not prevent members from battling or stealing artifacts from each other. Guild members fight together during Guild Wars, but a guild must have at least 5 members to participate in a war.
All members of a guild will gain a bonus energy amount equal to the member count. So for example, if you are in a guild with 37 members, your energy bar will be increased by 37.
This bonus stacks with energy packs that can be bought in the store for WB.
Guild Rating is calculated by taking the sum of all members' Battle rating divided by 100.
For example, if you form a guild when you have 17,022 Battle Rating, the Guild Rating starts at 170. If another player joins with 11,572, the guild now has 286 Guild Rating (170+116).
Guild Rating only affects position on the Top Guilds list, and has no effect on Guild Wars.
A Guild Leader can specify the guild name upon creation, and this cannot be changed later on. You can at any time edit the description, recruitment options (Open/Closed/Invite-only) and Minimum Battle Rating required for new members to join. Minimum Battle Rating can be any increment of 500 between and including 0 and 150000.
A Guild Leader can recruit new members from the Recruits screen, which shows a list of up to 20 players that are not in guilds and have a higher Battle Rating then the guild requires. These recruits can see a list of invites on the Guild tab. Guild Leaders can also search for specific players by name.
A Guild Leader can promote any other member to Guild Leader (which demotes the former leader to a standard member).
Guild Leaders can promote any number of members to the position of Officer. Officers can upgrade, swap, and repair Fortresses.
Officers can recruit like the leader but cannot kick members.
Guild can build Fortresses to aid them in Guild War. All members can earn GP by completing Event Quests, but only Leaders and Officers can spend GP to upgrade Fortresses, swap out Fortress cards, or use Repair Kits during a war. At the end of a war, all structures and GP are reset.