In my worldcanon, I am biased toward the elven creation myths, and my headcanons reflect it. One importance is my theory that 'mer who are older, closer to the original Aldmer, hold greater control and power over magicks. This can also be seen in many examples of mer throughout the games; Divayth Fyr, Mannimarco, among others. (Ilch considers himself among these 'mer.)
From the Monomyth: “As their aspects began to die off, many of the et'Ada....had to marry and make children just to last. Each generation was weaker than the last, and soon there were Aldmer.”
Ilchznch explains this as that the separation from Aetherius and the limiting of their magicks from being on Nirn. This is important to keep in mind as Thbza, as tested and concluded by Ilch and Nchen even when she was still young, is of a bloodline very close to the origin point of what was first distinguishable as a Dwemer. Due to this connection, she has immense potential power, as is shown in her ability to control the Earthbones, or, the laws of physics and nature on Nirn, the very essence of one's being—in her case, emotion.
The first Dwemer seem to have appeared in lage-middle Merethic Era. Perhaps, 1000 years before recorded history. The deeper into ME the 'mer was born, the more power they, theoretically, would have. It depends on how many generations there were between the Origin and the 'mer in question.
This is also why the Dwemer (and other 'mer) have a particular disdain for human folk; humans are seen to be extremely weak offspring of the et'Ada, which can be seen in many cases. Ilch has a particular distrust of humans (especially Nordic peoples, and especially the Companions) due to fighting Atmorans while defending his citystate of birth.
Thbza's voice is rather powerful. She has strong lungs and years of practice and building tolerance allow her to have impressive physical capabilities to sing. Even without sound magicks she is capable of projecting her voice over 100dB background noises, and is capable of holding a full note in excess of 60 seconds. While considered a lyric soprano, she can hold higher notes without stressing her voice for a surprising length of time.
After performances, she tends to her throat with teas formulated to ease the strain on her vocal cords. After more intense performances, such as a battle, she prefers to give herself a week or two to rest before performing again. Smaller shows and concerts she can do back to back for about a week before she takes off. She'll still practice soft scales or hum to herself on her off days so as to keep her voice limber.
The problem with Ilch's left knee is something he tends not to explain, since anyone can see he is in great pain and that does not need explanation.
When attempting to avenge Nchen's death, the end of his hydraulic-powered, extendable longstaff was knocked into direct path to extend into his knee. The force shattered the head of his femur, making it unrepairable. Surgeons were able to give him function of his knee by replacing the femur head with a metal prosthesis, anchored into the intact but sheared end of his femur.
This has always been painful for him to walk on, but lesser so when he was younger as some natural cartilage remained to give a small bit of cushion between natural bone and metal prosthesis. However, the years have worn away the cartilage and any attempts of his body naturally rebuilding it, and he now suffers from pure bone-on-metal scraping. Tapping his knee in any way can send a shock up his femur, and it is excruciating pain for him to attempt to stand on the knee without properly balancing himself—and even then it is severely painful as the metal digs into the bone it was fused with.
Anti-inflammatories and magickal pain guarding potions and the like are capable of helping this pain, but only subtly. However, taking the edge off is the best way to get a cooperative and less-grumpy Ilch.