You have a point there as well. He stated that after this elf mage said she didn't want to deal with demons anymore. It ties nicely with the fact that he told Briala not to get him the pass word. His boss couldn't get the PW without her.
So that implies that the demon needed to know the password, or that it would be difficult to obtain otherwise. That's weird, because you would think a demon that powerful would be able to just rip the answer straight out of Briala's mind, no problem. So either this Demon is very powerful, but limited, or there is some lingering magic of the elder days that is protecting Briala.
And now I'm wondering if Imshael and "The Master" are in league, or maybe rivals. Maybe that gem of Briala's is rigged somehow. Demons are not exactly known for their friendly and forthright natures.