HUBERT and CHRIS
The Crown and Titles. Hubert would marry the 'mad' Serenity, Chris would be made Regent or Overseer or something along those lines.
Having broken the mad Princess' garbled speech via quipquip. I proceeded to crack the code the old fashioned way: by hand.
I got close!
The Princess' garbled speech reveals that the alleged poisoner may be:
Hubert, the minister
Byby ryc tnihg buecuh! Cilr nybyledo, Ripand tacenac vydranc drnuha, yht so ryht... when decrypted reveals
Papa has drunk poison! Such rapacity, Hubert desires fathers throne, and my hand...
Using this tool https://www.dcode.fr/shift-cipher I spent some time using this alphabet:
ABDEFGIJKLMNPQRTUVWXYZSOHCand permutations thereof.
Then the comment by the author regarding the language came up a few hours ago....
I found this site: http://stefangagne.com/albhed.html
Clean clear translation.! Woohoo!
The numbers on the embroidered cloth can be decoded using a simple number-letter substitution cipher 1=A. 2=B, 3=C, ... ,26=Z
Top Row: 23 5 5 16 1 19 20 8 5 11 9 14 7 8 1
W E E P A S T H E K I N G H A
Right Column: 19 2 5 5 14 16 15 9 19 15 14 5 4 23 9
S B E E N P O I S O N E D W I T H
Left Column: 6 20 15 14 8 9 19 4 5 1 20 8 2 5 4
F T O N H I S D E A T H B E D
Bottom Row: 5 12 4 14 1 5 20 9 4 1 18 21 13 8 20
T H M U R I A D I T E A N D L E
Since this is a continuous loop that reads:
S B E E N P O I S O N E D W I T H M U R I A D I T E A N D L E F T O N H I S D E A T H B E D W E E P A S T H E K I N G H A
We can read the following:
Weep, as the King has been poisoned with Muradite and left on his death bed
This was definitely odd and probably put us all in many spins of the nog.
The pattern-of-flowers grid in the center of the embroidered cloth is not really a red herring as many might think and using the the same number-letter substitution cipher, reveals:
S B A I I T L G R L H A Y A P
Which when read diagonally reveals:
A BIG SILLY TRAP! HA!
Or is it...
In calling your attention quite loudly to the fact that it is indeed,silly, something starts to smell awfully fishy. And a lot of questions come to mind...
Why leave such details as revealed on the cloth, unspoken? Was Opal fearing for her life? What deeper or much simpler Machiavellian machinations were being deployed here?
Questions like these and other such conspiracy fueled tangents were crossing my thoughts...
At this stage, Hubert may or may not be the poisoner, but we do know that in any Kingdom the husband and wife are King and Queen. Perhaps Serenity's claim is not so mad.
Why the misdirection in the embroidered cloth?
Opal, as Head Maid, and probably the only person with access to the King's chambers and foods, would definitely need to be included in any plot against the King.
If this is the case (which I'm not sure it is), I don't want to speculate on what Opal was promised in turn for her help: but, if Opal was a key player in poisoning the King, why would she deliberately wipe the King's forehead with a cloth which implicated her?
Did someone give her the cloth?
After decoding the Princess' speech I went through a conspiracy theory where double-, triple- and even quadruple-reversals took place, before finally deciding to take the riddle at face value.
Chris is a royal knight but not particularly loyal.
Seen in this light, the Knight's rude and disrespectful attitude towards Serenity as well as the accusation that she was mad does paint a nasty portrait indeed. His abrupt tone to you the Royal Physician is also rather presumptuous.
Who would stand to gain most from the King's Death and the Princess' apparent madness?
Hubert and Chris
Hubert would marry Serenity making him the rightful heir through marriage and Chris would remain in his position, perhaps even given a promotion and titles.
In implicating the maid, Hubert and Chris reckoned that I would see this as a red herring and administer another drug, thus ensuring that the King died, leaving Serentiy mad to be manipulated at will.
What the conspirators did not count on was the fact that they threw the game in their interactions with me prior to the examination.
Hubert was rude and callous and disrespectful towards the Princess and it seemed that he was nervous about something.
Chris man-handled Serenity, cutting her off before she could say anything else. Passing her comments off as those of a mad-woman and urging me rather rudely to finish the job, hoping I would be misled by the various booby-traps along the way.
Their conversation, was highly suspicious.
I was toying with the idea of the antidote being
SABUETTE, on the strength of the 8-digit words, 'MURIDATE', 'SERENITY', 'ANTIDOTE' as well as my own attempts to crack the foreign tongue on the link provided. Using 30, 15 and 8, I did get close to encrypting it to the letter, but I just couldn't get it right.
Hubert/Chris probably gave the cloth Opal who was unaware of the messages revealed. The cloth was prepared long before the event.
Why Serenity is not dead, is due to the fact they need her alive but unable to rule. She did imbibe a very small dose of poison administered via her food or drink at some point during the day and the phrase "she drank from the goblet" was just a ruse.
SOHC were used in the substitute cipher attempts as it is the initials of their names presented very clearly elaborately in point form.
Perhaps if I had tried and of the drugs or antidotes in other alphabet attacks on the cipher text I may have been successful.
Thanks to @Mhmed for pointing out
First letter of each spoken phrase is very close to
I hope @Asteria gives us a walk through.
The King Lives - Long Live the King