Chapter 150: Becoming the public enemy of Serenity Town Part 2
"Why did you run though?" Kayn can't help himself from asking. As far as he knows, it is practically impossible to see Natas unless the latter intends to show himself, even the 'Tower' isn't excepted from this, so how could a Monster see him?
"The Monster didn't spot me, but I can't afford to compromise the Storage Ring,"
That's right! Although Natas couldn't be seen, the Storage Ring can.
If Natas was holding the Storage Ring, people would only be able to see the ring moving and levitating around, making it appear as though it is floating on its own. This is why if the Monster were to spot the Storage Ring, it would likely pursue it because it would assume the Molten Magma Core is contained within. However, the monster would be unable to see Natas himself.