Guilds were once major adventurer-run organisations which wielded great latitude over the classes of Achaea, often a time colloquially referred to as the Guild Era. For centuries, in fact, the term "Guild" was used interchangeably with "class", in which the Guild one belonged to determined one's class and vice versa. Centred around common skills and ideals, Guilds were led by a Guildmaster and his or her appointed secretaries. In the year 399 AF, however, Guilds became officially obsolete as these organisations underwent conversion to Houses.

The following are the former Guilds of Achaea and their respective classes, listed in order of their conversion to Houses:

GUILD CLASS HOUSE
Sentaari Monk The Sentaari(destroyed)
Sentinels Sentinel The Sentinels of Nature
Kharon Monk The Sect of the Black Lotus
Druids Druid The Ancient Circle of Druids
Paladins Paladin The Guardians of Light(destroyed)
Serpentlords Serpent The Cult of the Serpent Lords
Occultists Occultist The Occultists
Priests Priest The Empyreal Assembly(destroyed)
Shadowsnakes Serpent The Shadowsnakes
Magi Magi The Crystalline Circle(destroyed)
Warlocks Magi The Warlocks of the Rising Phoenix
Dawnstriders Serpent The Dawnstriders(destroyed)
Ashura Monk The Ashura
Runewardens Runewardens The Wardens of the Cerulean Spire
Mojushai Monk The Mojushai
Maldaathi Infernal The Maldaathi
Naga Serpent The Naga
Apostates Apostate The Blood Congregation
Sylvans Sylvan The Sylvanic Fellowship
Tanjinn Monk The Ebon Fist
Bards Bard Ty Beirdd
Shamans Shaman Spirit Walkers
Sorcerers Magi Merchants of the Crown
Arcanists Magi The Arcane Kindred
Jesters Jester Carnivalis Institute of Jestering
Infernals Infernal (destroyed in 299 AF)