Upon seeing the door constructed entirely from anti-magic materials, Irving and Nick displayed distinctly different expressions.
Irving was filled with excitement, believing that finding this door meant he could finally access the underground area. This represented the opportunity to resolve the last remaining threat within the castle. His mood was therefore quite exhilarated.
In stark contrast, Nick felt very uneasy. To him, anti-magic materials were incredibly rare and valuable. Even the Angel Guild would struggle to amass enough of these materials to create such a heavy door. Moreover, members of the Angel Guild generally believed that anti-magic materials were used to construct seals for magical formations.
A door made entirely of anti-magic materials could very well be the core of a seal for a magical formation, which meant that opening it might unleash an exceptionally terrifying monster.