Maybe I'm missing something? Then – especially for the slow-witted – maybe you should make the hint more specific? And, at the very least, suggest that you should experiment with the mentor regarding Aschi's patronage (if, of course, you need to dig)...
And once you think about the return journey, it becomes even more depressing. They could have at least added a fort near the second entrance to the dungeon – the "Portal" spell is just wasted. I spent 10 months looking for it...