Louis Cal Lamar, king of the coastal realm of Calara, was dying. Not quickly nor gently, but in slow, agonizing illness that ravaged his body daily; pulling, twisting, and distorting his muscles and bones. No medications, poultices, or treatments prescribed by his physicians could help him. At fifty-seven years old he was a wasted and pitiful remnant of his former self. His flesh was melting away from his body at an alarming rate, leaving him little more than a skeletal, shadowy form. Fingers that once grasped a weapon or strummed a harp now trembled and jerked with involuntary spasms. His once regal walk was now marked with halts and shuffles. His orator’s voice had fled, leaving a cracked and squeaky squawk in its stead. Had he also begun to lose his sanity as well, this condition might not

There are a lot of places where you have pairs of adjectives/verbs/adverbs (e.g., quickly nor gently; pulling, twisting, and distorting; cracked and squeaky). I think the paragraph might be stronger if you picked just the most crucial word instead of including so much detail.

The last sentence has a lot of potential, but the wording is a little bit cumbersome for me (my brain is tired today, and had a hard time keeping track of 'they', 'if', and 'had'). But once I processed the sentence I liked that it suggests that there is something odd about the illness, and that it has an ominous note to it.

(Just to avoid confusion for people reading the post later--the last sentence that I was referring to was trimmed out of the original message)

I didn't care for this, but I didn't find it awful. I think what I didn't like is that it's summary, but it's a summary that goes on and on. If you want to summarize, I suggest brevity: "King Whatshis was wasting away." When you're ready to show us something, put us in the moment.

I did not have a strong emotional response to the opening. I felt as though I should feel very sorry for the king, but I did not. Perhaps it's just me, or perhaps the use of the omniscient POV to describe personal suffering lacked some of the emotion that could be found if we were experiencing the decay through the king's eyes.

I was also a little disappointed that there was no parallel between the king's state and the state of his realm. I would have liked to learn something about his subjects and their reaction to the king's decline, or learn something about the symbols of the Calarian kingship. Does he wear a special Calarian crown that has grown too heavy for his head? Can he no longer climb the steps of the great bell tower? ect.

For style nits, the liberal use of adjectives/adverbs has already been mentioned. If I were revising this section, I would start by eliminating adjs/advs that repeat information already given in descriptive nouns/verbs (ie. "squeaky squawk"- can we assume that most squawks are squeaky and leave out the squeaky?) If there are still too many adjs/advs, then you could replace less descriptive nouns/verbs with more descriptive ones.

One further nit:
"Had he also begun to lose his sanity as well"
"as well" is just a repeat of "also"

I tend to overload the first drafts of my writing to set the mood and direction of the story line, then pare it down in the revisions.

*edit*

I have to confess I have a little trouble with POV. The lines actually are the POV of Louis' son, Lawrence, as the next paragraph reveals.

Of course, this would make me much more interested in the son, Lawrence, then in the king, and that might not be your intention. If the relationship between the father and son has been fairly well explained in the previous books, you could use that initial sentence to simply restate that--have Lawrence act as he would be expected to, or as he already has frequently when visiting his father. Since nothing new is actually being presented to the reader, the focus doesn't shift from wherever it was in the previous book(s), and the scene simply serves as an excellent establishing shot.