Mysterious Artifact

Exploration Stage: Station
From: Juliette
Description: While you were bravely fighting the gargoyle, a mysterious stranger passed me this note. "Look for a fang on the border between worlds. Signed L." Jacob was wearing a fang around his neck, you say? But I don't get what "border between worlds" means. Maybe it's the Station? Since all newcomers to the City of Shadows appear there. Explore the Station of Forgotten Dreams.
Completed: This is a Gargoyle fang - an artifact from the City of Shadows! Where did your friend get it from? If it was on him before you two even ended up in the City, then how did Jacob come across it? Like the photo, this fang is confirmation that your friend is connected to the City and the House with red Windows.