A guild is a community of players who join forces so they can participate in guild battles, help each other retrieve stolen gems, test each other's dungeons and simply chat. To join a guild, you must first finish Wooden League. Guilds can be found in League menu (the one with the leaderboard). You can find a particular guild using a search function, join the guild of your friend in "Friends" section or create your own guild in "My Guild". The latter will cost you 200.000 gold coins.