Aliens in the sewers. Remus had no idea how to imagine them, as the only visual that keeps popping in his mind is a green troll marching down the the pipes. That was a thing for thought...
"We," he began after a sip of coffee, "back home, I mean, we are not new to creatures as well. We ourselves have many: trolls, ogres, ghouls...and I am not sure if Mu-- if you," he had nearly called her a Muggle, how embarrassing, "would know...but we have mm...dementors, boggarts...grindylows, kappas, we have many. I am yet to see any of them here but..." he looked around the table in search for something, his left hand moving indecisively as though to steal another sheet of tissue. "There is something..."
Giving up, he decided on simply talking to Gwen about this something. "Have you seen someone wearing dark robes this late? Long dark robes with...or they might give up their robes for something more ordinary-looking...but they might have a mark on their forearm." Remus paused as if to let Gwen understand what he was saying. "A skull with a snake slithering through an open mouth, a dark mark. Have you seen one?"