Adamas is an heavenly metal found beneath Idris used to make tools for Shadowhunters. They are forged by the Iron Sisters, the only ones capable of handling the material. It is referenced in this episode.
In the novels, Sister Cleophas is Luke's mother. In the TV series, she's his sister.
In a deleted scene, Jace found that his clearance and access to Clave records have yet to be restored. In the scene, Alyssa Capriotti made her debut as Lindsay.