I don't get the thought process, but... I'm not saying you're wrong. 

Seeker Mun taps one finger against her lips.

“Time I see a little but the door is an ear, and we must not lose sight of that. Perhaps it is words, or reputation or judgement or law. I feel like it is something not far from this but can’t quite capture the perfect term.”

”Testimony? Evidence?”

“Truth. Truth I can see.”

(It’s times like these I’m glad to play an average intelligence character to complement my average intelligence. Good luck Preyfire!) 

Quote from NycrolB >>

Seeker Mun taps one finger against her lips.

“Time I see a little but the door is an ear, and we must not lose sight of that. Perhaps it is words, or reputation or judgement or law. I feel like it is something not far from this but can’t quite capture the perfect term.”

”Testimony? Evidence?”

“Truth. Truth I can see.”

(It’s times like these I’m glad to play an average intelligence character to complement my average intelligence. Good luck Preyfire!) 

 {Same. I had a game once where you could use intelligence checks to get hints. Maybe shiver will allow?}

[I'm happy to allow an intelligence check if you feel you've exhausted all options, but I will say for free that you're on the right lines at the moment and have been very close.]

(I’ve been thinking about this a lot through the day. The mouth needs to eat. The eye is a peephole. And the ear needs to hear a riddle? Is that enough? Or is the riddle needing to include a ‘sound’/‘hearing’ related answer too? Because if not then lots of more vaguely similar answers to before like Revelation become apparent. But none of them feel right in the way that just makes you think ‘Ah, I’ve got it’. That certainty). 

Sly muses over the riddle for a while.

"To me it seems, the answer should be faith.", she says eventually.

The wizard carefully moves about the room, studying the writing, being careful not to touch anything. It seemed fairly clear what the ear and the mouth wanted, so the eye annoyed her the most. What manner of trap did it contain?

Sly uses her mage hand to lift her staff and poke it in the eye, tapping up and down. She tries to get an idea of how deep that eyehole is.

Daewen observes the exchange, her gaze thoughtful as the team throws out suggestions.  Once Mun proposes "Truth," Daewen offers a small, almost imperceptible nod of agreement, the concept aligning with her own earlier thoughts of "WORDS" conveying information.  She scrunches up her nose in deep concentration, her brow furrowed as she continues to ponder further solutions.  Her slender fingers begin to move subtly in the air, tracing the shapes of imaginary letters, as if the act of writing might help her unlock the riddle's secret.

Intelligence check: 4

(OOC: Yeah, Daewen just stares like an idiot into the gloom with that low INT check...#dumpstatINT)

{{OOC: Shiver, you said that the eyehole was 3 feet wide. Can Bilyur stand up straight inside the tunnel? If he entered it, what would his darkvision let him see?}} 

((I have been studying the riddle off and on and one other idea popped in my head. This is the dungeon of terror. What do you guys think about the action word being FEAR?))

Daewen tries her hardest but can't come up with any viable solutions to the riddle other than the one she originally devised. Whilst she does struggle to uncover any hidden meaning to form new answers, one of her main difficulties comes from putting aside the answer of 'words', as that seems to be the most fitting option in her mind. 

[Bilyur can indeed stand straight up in the tunnel. If he got in, he wouldn't see much else compared to Xarkris; it's fairly nondescript]

((Fear fits. What do we go for. My suspicion is that the wrong answer will get one of us darted)). 

((OOC: I have always found that if inspiration is not to be found, one must do the work to get it out. I took 6 of the answers proposed by the members and I would like to fit them in the riddle to see which one matches the most clues.

If you wish to pass this door you must speak aloud my name 
I can have a thousand faces but at my core (CLOCK, GOD, TRUTH, EVIDENCE, FAITH, FEAR) is the same 
Though a friend of saints and devils, (CLOCK, GOD, TRUTH, EVIDENCE, FAITH, FEAR)'s source remains unchanged 
Yet (CLOCK, GOD, TRUTH, EVIDENCE, FAITH, FEAR)'s nature can define the split between the genius and deranged 
With kings, (CLOCK, GOD, TRUTH, EVIDENCE, FAITH, FEAR) can bring power, with thieves, (CLOCK, GOD, TRUTH, EVIDENCE, FAITH, FEAR) can bring death,
And with feuding lovers (CLOCK, GOD, TRUTH, EVIDENCE, FAITH, FEAR) can leave them mended or bereft

I think FEAR is the best answer so far and fits all of the lines.))

Sly has the highest INVESTIGATION ability (I think), so Xarkris uses the ACTION of AID and assists Sly in attempting an INVESTIGATION check (if she wishes), giving her ADVANTAGE in her attempt to get a clue or hint from the DM.

(OOC: “Time”?)

Sly will have a good think about it again, trying to see if she missed anything in her first analysis of the riddle, discussing it with Xarkris: Investigation check with advantage: 19

{To me, Evidence is actually the current option that seems to fit all the lines the best. 

If you wish to pass this door you must speak aloud my name 
I can have a thousand faces but at my core EVIDENCE is the same 
Though a friend of saints and devils, EVIDENCE's source remains unchanged 
Yet EVIDENCE's nature can define the split between the genius and the deranged 
With kings, EVIDENCE can bring power, with thieves, EVIDENCE can bring death,
And with feuding lovers EVIDENCE can leave them mended or bereft

as for FEAR

If you wish to pass this door you must speak aloud my name 
I can have a thousand faces but at my core FEAR is the same  (I understand this) 
Though a friend of saints and devils, FEARs source remains unchanged (I don't understand this) 
Yet FEAR's nature can define the split between the genius and deranged (I don't understand this) 
With kings, FEAR can bring power, with thieves, FEAR can bring death, (I understand this) 
And with feuding lovers FEAR can leave them mended or bereft(I don't understand this) 

Sly finds that the eyehole only goes 20 feet before opening up into a room with her mage hand, and can't identify any traps in the tunnel. She then thinks more on the riddle, and starts to get a firm grasp on what it could mean. She starts with the root hypothesis that it would be reasonable for the riddle to have a sound related answer, since it is an ear, to narrow down the options, Already this rules out several options proposed by Xarkris, who is giving her help by providing options. In particular, seeing as its the party's best guess, she can rule out fear by analysing the line 'my source remains unchanged.' Fear is the pure opposite of that, seeing as it can come from a manner of places. 'A thousand faces' means it can take on a multitude of meanings; that's clear, and as it is a 'friend of saints and devils' it must be impartial, or its 'thousand faces' can range from absolute good to evil. The fact that 'its source remains the same' implies it can't be words like Mun first thought, as those can be both spoken and written, and if she sticks with her running theory of it being sound-related, that means it must be verbal. Then, there's the fact it can define 'the genius and deranged'. Surely that implies it can be manipulated by anyone from genius to madman, though the way they use it is a key part of their identity as such. Truth fits very, very well, aside from the fact that it isn't the friend of devils, and could also be written. So, in conclusion, it's something verbal that can have any meaning from good to bad, which can be used by almost all, and the way it is used can lead to a variety of outcomes. 

Sly eliminates one theory after the other, methodically ruling out the concepts that contradicted each other.

"It seems that the solution is a vocalization that can't be easily replicated in another form. To bring death to a thief, it could be a potentially involuntary one, like laughter. The nature of laughter can certainly also separate a genius from a maniac. But it doesn't fit bringing power with kings. And screams, moans, cries and sighs all don't make as much sense..."

The wizard trails off. It was clear that she hadn't arrived at the solution either, and it bothered her great mind a great deal.

[I thought about it quite a bit, but no dice]

I still don't get it. I'm going to go down the tunnel. If I die, I'll see you later as a different character. XD! 

“Speech,” says Mun.