The people of the Tieba City had been watching everything that had happened this whole time. Their original plan had been to observe the expedition group and to take away their gains when they finally succeeded.
And if they did not manage to do this, it would still be death for them. After all, it would simply mean that the people were too strong for them to overcome, which they already knew was impossible.
Originally, they had been wanting to be the oriole that stalked the mantis stalking the cicada. In this case though, the cicada was the tomb underneath the ruins that existed here for many years, while the mantis was the expedition people who came to look for it.
But shocking to them, the cicada that they were so looking forward to turned out to not be a cicada at all. Instead, it was a monster that ate the mantis and could very easily devour them as well.