The unjoined Trill who devote their lives to tending the symbionts in the spawning pools beneath the Trill homeworld.
The Guardians are unjoined Trill who care for the symbionts in the caves beneath the surface of Trill, tending the pools where the creatures live until they are joined. Their role gives them an intimate, almost spiritual bond with the symbionts.
Benjamin Sisko and Julian Bashir sought their help when Jadzia Dax's symbiont was in crisis in 2371. Centuries later, in the 32nd century, a Guardian helped Adira Tal reconnect with the memories of the Tal symbiont, showing that the order had endured through the Burn.