Waif assassins were waifs who were employed as hitmen to kill the enemies of those who used their services. Their ability to hear the thoughts of their victims allowed them to easily hide and launch surprise attacks. Typical weapons of choice for waif assassins included small daggers and blowpipes which fired poisonous darts.
During the events of Clash of the Sky Galleons, Thaw Daggerslash hired a nightwaif to murder Wind Jackal at the Sluice Tower, but was thwarted by Menisculis, who stabbed the would-be killer in the chest just as he jumped out of the shadows.
Hundreds of years later, during the events of Weird New Worlds, Quove Lentis employed a waif assassin to kill Hedgethorn Lammergyre before he could reveal the high professor's treacherous actions against the Farrow Ridges. Luggins jumped in front of Hedgethorn to take the dart instead, and was killed instantly. Before the waif assassin could shot another dart, Threnodesse fatally stabbed him from behind.