Nereids are a race of water-dwelling fey, distantly related to dryads and similar to sirines. Like dryads, they are powerful spellcasters, combining an innate ability for Charm Person spells with an arsenal of combat spells.
In Baldur's Gate[]
A single nereid, Shoal, appears at the Shipwreck's Coast, though she counts as a monster, rather than a humanoid.
In Siege of Dragonspear[]
Another nereid can be encountered during the events of Baldur's Gate: Siege of Dragonspear as part of the quest Strunk's Elementals in the Underground River.