Atlas went directly into training and planned to spend the majority of his time in the Xuanying Treasure Pagoda, but getting stronger wasn't the only thing he needed to do.
According to the Hell Guardian, the reason he could not yet challenge it was not his strength, but the strength of his Society Legend. Naturally, if Atlas holed himself up inside of the pagoda, he wouldn't be able to contribute to the growth of that Legend.
Well, in a certain sense, he didn't have to.
While he was moving on his own, the conflict with Dusk didn't quiet down. It got louder, to the point where it was the talk of the lower floors.
Pangea's emblem was public knowledge now, and even the name Pangea was starting to spread through the grapevine, but nobody knew who its members were.
People could only find that it was a new Society with a very apparent grudge against Dusk.