There was a Fallen human here. Simply put, it was a double-pronged attack. After coming to a scene, Heroes went to the most dangerous area. Since the Artifact Room had security guards, it was less dangerous comparatively, putting it on a lower priority. Taking advantage of this fact, the Fallen human attack here.
This all of doing fallen human, he had receivedoleanderr from his contractor a demon with whom he made a pact.
The monster outside is also in his control, and because of that Heros has a hard time killing it, thus not reaching herein time.
As panic and unease gripped the Artifact Room, Adrian, Isabella, and Lucas exchanged concerned glances. The chaos outside continued to escalate, with the thudding footsteps growing louder and closer.