Go to Beadeaux and head through the underground area. Go back up to the upper level using the ramp, across the small then large bridge to the north side of G-10. The NPC Ge'Fhu Yagudoeye is located by the smokestacks.
Clear the surrounding Quadav near him, then talk to him to spawn four NMs: two Nickel Quadav (Paladin) and two Magnes Quadav (Black Mage). They can be slept and silenced (very high resistance to Silence) to make the fight easier; the Magnes Quadav have far fewer HP and should generally be killed first.
Kill the four NM Quadav and then talk to Ge'Fhu Yagudoeye for a cutscene. If the cutscene does not appear, re-zone into Beadeaux to receive it; however, it usually triggers. If multiple people are doing the quest at once, it is necessary to respawn and kill the NMs for each character who is on the quest; they can be spawned without zoning, by each different character, about every 5 minutes from the NPC.