Ghoul guard

s are seen guarding the Museum Authority Building from people looking to learn the secret of Aqua Cura. It is also explained in the note Griffon's Bottling Instructions that they are the ones who pick up the Aqua Pura deliveries from the Brotherhood of Steel and dilute it to make Aqua Cura.

They appear as hostile towards the Lone Wanderer

Appearances
s appear in the Fallout 3 DLC Broken Steel.