Why didn't Vikus tell Gregor about the rats right away?

[Marlene]

Because it wouldn't have been such a dramatic reveal of the rats if the Underlanders had just told Gregor. ;)

[Janie]

Good question. I think that maybe it had to do with the fact that it never really came up in conversation. I mean, can you imagine? "Welcome to the Underland! There are huge man-eating talking rats down here!" Gregor was already freaked out, and he never really asked for a list of dangerous things or anything, and the rats were just a normal part of Vikus's life that he may have not considered to be super important. He had the whole "woah, overlander of the prophesies" thing to consider, and he probably wasn’t expecting Gregor to run.