The Kuo-Toa are a hidden race in Baldur's Gate 3 that are already tough to find. Those who find their secret entrance will realize why they aren't wandering the world and trading on the surface. They are enraptured by a god named BOOOAL, making live sacrifices and endlessly praising the incarnate god.
Baldur's Gate 3: How To Save The Kuo-Toa From BOOOAL
The Kuo-Toa are rare enough as it is in Baldur's Gate 3 and they can easily become extinct without some quick thinking by the players.