It was indeed during Harrogate. The young fool decided 'twould be best for him to investigate the events at the sinkhole on his lonesome. He was arrogant enough that he did not bring back-up. And because the villain was no longer the Ghostly Emperor's Grand Vizier, but the malicious god who possessed her, he was murdered first for his troubles and then had his spiritual body devoured. It was only his ability to place his mind directly onto the network and sustain himself in such a space that allowed him to advise us with his dearly bought intelligence later.

... it is not that I am ungrateful that he did, mind. It is only that it doesn't change the fact that he was still a fool to go alone--and that it broke Alcuin's heart when he thought Armin was dead.