The Guild Council was the legislative body of the D'ni government. It consisted of representatives from each of the 18 major guilds, and was presided over by five Great Lords. During the time of the kings, the Council operated like a parliament in a constitutional monarchy: able to propose and pass legislation, but also subject to being overruled by the king on certain matters. When King Kerath abdicated the throne, he ceded all power to the Council, granting them full control of the D'ni government.
To be a member of the Guild Council, a guildsman had to be a Guild Master in their guild. Of the many Guild Masters in each guild, only a handful served on the Council, and were elected as representatives by their peers.
In addition to the Guild Masters elected to serve on the Council, each guild's Grand Master also served as a representative of their organization. The 18 Grand Masters were sometimes referred to as the High Council. It is unclear if the High Council had any special power that the full Council did not, though it seems that they were able to set the agenda for what would be discussed at Council meetings.
The Great Lords
Presiding over the Guild Council were five Great Lords. The Lords were elevated to their rank from Grand Master, and appear to have held their position until death. Any of the 18 Grand Masters on the Council could succeed a Great Lord, possibly by vote, though the exact process for succession is unknown. When a Grand Master became a Great Lord, a new Grand Master was chosen from among the Guild Masters to lead that guild.