...is that obvious to a casual inspection?

The depressions are basically the same size and shape as each other, but if Nenio's hypothesis is correct it's possible that the masks they're supposed to use have some other non-shape-based characteristic that distinguishes them. The masked strangers' masks are nearly identical, solid white with holes for their eyes and mouths, with minor differences where some have larger heads than others.

"All right, do you have an immediate prospect of solving any of the riddles?" Blai asks Nenio.

"Regrettably, I do not." Pause. "However, if other experimental subjects touched the statue, it could provide us with additional information about the entity that spoke to me, although it is possible my account will affect the results."

"Your repeated return to this concept is not easing my mind about whether the experience might have subtly enchanted you."

"That hypothesis is testable. Detect Magic." She looks at her — hands? paws? — for a few moments. "I do not see any enchantments, unless they have been concealed by magic."

"I am reasonably confident you can figure out the problem with this exact method but as it happens the other wizards did not remark on any enchantment either, so it would have to be a hidden one."

"With how strong the illusion was, I'm not sure I would have seen a little enchantment even if it weren't hidden. ...although we'd probably be able to see it now, if it weren't hidden, and I don't."

Are large numbers of mysterious masked people still just standing around staring at them and not saying anything? That's getting to be really weird. When they encounter them on walkabout they seem at least slightly responsive to their surroundings.

The mysterious masked people have not said anything, apart from the one who disappeared. Some of them are slowly turning their heads to track when people in Blai's party move.

"Excuse me," he says to the nearest one who is at least looking at them. "Can you shed any light on this situation?" It will not work but it probably also won't make anything worse.

"The absence of an answer is an answer too."

Yeah that's about what he was expecting. "So you think that this puzzle involves collecting objects, do you have any way to guess where they might be or recognize them if we find them?" he asks Nenio.

"Unfortunately, I am not aware of an obvious way to locate them, considering our current level of information. Whether I am capable of recognizing them if we find them will depend on how skilled the puzzle's creator was at constructing puzzles."

"They might not even still exist, this place looks old as fuck."

"That would be highly unfortunate."

"What is your basis for the belief that it would help to have someone else touch a pillar?"

"I do not know whether it will be of use in solving the puzzle! Its primary use would be in learning more about the entity who is associated with the statue. For example, if the entity presents itself in a radically different manner depending on the individual with which it is speaking, that could suggest that my relatively positive impression was misplaced."

"I am a little surprised you find such an unforthcoming entity worthy of your positive regard."

"I would certainly find it preferable if the entity were willing to participate in an interview! Nonetheless, it is skilled in wielding powerful magic, capable of communicating hitherto-unknown information, and interested in puzzles, all of which are positive traits."

Headtilt. "...Maybe we could come up with puzzles for you? But I've never done it before, so they might not be any good."

"I do not think the upside potential of touching the statue is worth the risk that it will have wide behavioral variance and do something untoward in response to a second approach, so perhaps we've done all there is to do here."

Her fox ears droop a little. "Perhaps we will have the opportunity to investigate more thoroughly if we can locate the necessary items."

"Do you have a proposed next step toward that end?"

She contemplates this. "Perhaps if we observe any of the mysterious strangers walking away from this place, rather than in its direction, we could follow them. But I am not confident that this would be fruitful."