The Toxcatl ceremony and ritual was an event for Tezcatlipoca dedicated to him and his representative on earth the Ixiptla of Tezcatlipoca he would be carefully chosen out of a very demanding list of attributes but most importantly he had to be handsome, young, fit, intelligent. He would be given four wives representing Xochiquetzal, Huixtocihuatl, Xilonen, Atlatonan, as well as immense social power and wealth some say even more power than the king himself. It was an extremely high honor to be chosen as the Ixiptla of Tezcatlipoca, Tezcatlipoca being described as the supreme god of the Aztecs in the Florentine Codex. Being sacrificed in Mexica(Aztec) society was not seen as a bad thing. It was an honorable way to die for a captured warrior or Ixiptla. An ordinary man or woman who died would have to struggle through various layers of underworlds being 9 in total, prior to meeting their rest. A sacrifice would avoid all that, along with warriors who died in battle and women who died in childbirth, they avoided all that by directly transcending .After a year of being the Ixiptla of Tezcatlipoca the Ixiptla would be sacrificed.
Florentine Codex Toxcatl Passage: "Thus it was said when he arrived where the Ixiptla of Tezcatlipoca used to die, where a small temple called Tlacochalco stood, he ascended by himself, he went up of his own free will to where he was to die. As he was taken up a step, as he passed one, there he broke, he shattered his flute his whistle. And when he had mounted all the steps, when he had risen to the summit, then the offering priests siezed him, they threw him upon his back on the sacrificial stone; then one of them cut open his breast; he took his heart from him; he raised it in dedication to the sun. For in this manner were all captives slain. but his body they did not roll down; rather they lowered it. four men carried it And his severed head they hung on the skull rack. Thus he was brough to an end in the adornment on which he died. Thus his life there ended; there they terminated his life when he went to die there at Tlapitzauyan. And this betokened our life on earth. for he who rejoiced, who possessed riches, who sought, who esteemed our lord's sweetness, his fragrance, richness, prosperity, thus ended in great misery. indeed it was said noone went exhausting happiness richness wealth." -Florentine Codex
Toxcatl
The selection of Tezcatlipoca's Ixiptla began during the time of the previous Ixiptla of Tezcatlipoca. As captives were taken, those who were deemed suitable candidates were set aside and looked over by a group called calpixque they were like tribute or tax collectors that oversaw conquered areas for the Aztecs. The meaning of the word is something like "protecter of a house/caretaker". In this case, they were something like an administrative class tasked with protecting and guarding the ixiptla of Tezcatlipoca the group was likely made up of experienced, veteran older men who might have even taken the captives themselves.
From this small selection of candidates they had to choose the most beautiful and perfect one both in terms of physicality and intelligence, the earthly representative of Tezcatlipoca selected was expected to be perfect, in physical form as well as aptitude and bearing. There's an absurdly long and precise list of all the physical attributes the candidate was expected to have, or not have since the list rules out extremes on both sides. He couldn't be too tall, or too short, too thin, or too fat. Here is the passage on how the head of Tezcatlipoca's Ixiptla should look:
"He was not long-headed; the back of his head was not pointed; his head was not like a carrying net; his head was not bumpy; he was not broad-headed; he was not rectangular-headed; he was not bald."
This is just the head, not the rest like the neck, forehead, nose, eyes, ears. chin, teeth all of which are individually described in a similar fashion along with various other body parts. Some other parts though like having a "carrying net" or a having a forehead "like a tomato" are not very clear and somewhat open to interpretation.
Only the most beautiful man was chosen, while his physical aspects were closely examined and highly valued he was also expected to be "of good understanding, quick." The Ixiptla of Tezcatlipoca for a year spent his time as a divine representative or Avatar of Tezcatlipoca as well as a travelling musician-poet, he needed to be intelligent as well as attractive. He also had to speak the Nahuatl language. He also instructed on everything that would happen to him and the rituals and ceremonies surrounding it.
There's two accounts of where the Ixiptla of Tezcatlipoca lived the year leading up to his sacrifice, according to Sahagun the Ixiptla lived with the stewards while he was instructed in the behaviors expected of him. But Duran claims that he lived in the inner sanctum of Tenochtitlan’s Temple of Tezcatlipoca .
It was most likely both. With the ixiptla starting his divine life in the direct care of the stewards before moving into the temple like a proper god once he was prepared and ready.
The earthly representative of Tezcatlipoca had several items which were almost exclusive to Tezcatlipoca. His Smoking Mirror being the main accessory his obsidian mirror carried or worn on the chest, his flute and his smoking tube or pipe. He would be decked out with an elaborate feathered headdress most likely of quetzal feathers due to his divine stature and carrying a shield, though this was most likely decorative and not a functional shield or yaochimalli.
He went everywhere constantly covered in feathers and flowers, playing the flute, and dancing. In the picture of Tezcatlipoca's ixiptla on page 183 of the florentine codex (look at page 180 for the beginning of the Toxcatl passage.)depicts him in a full tlahuitzli, wearing a mask or heavily painted face, and wearing a garland of flowers which spills down to his shoulders. Tezcatlipoca's ixiptla would visit the Huey Tlatoani several times during his year as Tezcatlipoca, he'd be received warmly given a lot of jewelry and things of high value. Items mentioned are gold upper armbands, turquoise on the lower arms, golden shell pendants on the ears, turquoise plugs though the lobes, shell necklaces, a snail shell labret, a fine mesh mantle with cotten trim, an extra long breechcloth, sandals made with obsidian and ocelot ears, and golden bells all up and down his sides and legs. It was an extensive amount of gifts the extensive amount of jewelry seems like it would've limited a normal person's movement due to the weight of it.
All of this, would be shed prior to his sacrifice.
The role of the ixiptla of Tezcatlipoca was to be Tezcatlipoca until he was sacrificed, he really had no other recorded duties other than learning to fulfill his role as one of if not the most important Aztec God. During this time he was given all the privileges of a tecuhtli ( high ranking lord) though he was respected far more than any other tecuhtli. The people who saw him in the streets would bow and, wetting their fingers and touching them into the dirt, pressed them to their lips in a particularly Nahua form of respect. They would ask for his favor of the ixiptla of Tezcatlipoca.
Then he would continue his wanderings. He went wherever he wanted within the city freely and at will, playing music, singing, dancing, reciting poetry, and enjoying life. Quoting Sahagun:
"Thereupon he began his office. He went about playing the flute. By day and by night he followed whatever way he wished."
Tezcatlipoca was provided with a group 12 people: eight servants and four veteran men. This arrangement obviously had practical everyday uses like protection and gave a sense of grandeur to anyone in the presence of Tezcatlipoca's Ixiptla. These servant and constables were pretty much his jailers though. They were there to ensure that he maintained his role and much as they were there to also protect and serve him.
If an Ixiptla ran Duran says that if he did escape, the guard who allowed it would take his place. Nothing of this sort is in any of the other early sources and this would be a severe breach of the elaborate protocol of choosing an, ixiptla so this may be a mistake or over exaggeration by Duran. Overall, the attitude of those chosen appeared to be accepting of the high honor of being the Principal God Tezcatlipoca's Ixiptla his earthly representative.
One vientena (a 20 day month) prior to Toxcatl, Tezcatlipoca would shed all the finery he had gained. He'd begin by fasting and cutting hair in the style of a warrior, he was also be given quetzal ( symbols of divine or royal status) and heron feathers. Carrasco sees this as part of the metamorphic quality of Tezcatlipoca. He arrived as a captive or slave who was then elevated to a position of otherworldly divinity and presence. Now he was simply a warrior on his way to being a captive, a sacrifice, yet again. This represented the sweet but ultimately ending nature of life. Its the Nahua concept of in xochitl, in cuitcatl (flower and song),
Tezcatlipoca's Ixiptla, as a man and warrior, was married to 4 women (the number 4 is heavy with symbolism in Mesoamerica so it might be because of that for example the four cardinal directions and the four Tezcatlipocas) the ixiptlatin of Tezcatlipoca's wives were serving a year as Tezcatlipoca's wives the goddesses Xochiquetzal, Atlatonan, Hictocihuatl, and Xilonen. His wives were powerful Goddesses of femininity, beauty, flowers, fertility, water, earth rebirth, and agriculture. The festival took place in May, when the long dry period of Mexico was coming to an end, but summer and early fall hadn't hit yet. This was period in which streams dried up, rivers were turned to trickles, and the lakes were at their lowest, sometimes drying into separate lakes altogether. Toxcatl meaning dryness, in other words, was a time of change and uncertainty both spiritually and agriculturally.
Five days before Toxcatl though, Tezcatlipoca and his wives would begin a religious pilgrimage. On each day they would visit a different shrine, praying, dancing, and singing. On the final day, Tezcatlipoca would separate from them and be given his farewells by his wives. Having enjoyed his time as Tezcatlipoca's Ixiptla, his divine representative on earth having enjoyed the respect of the people as a supreme god's avatar he was now ready to be a sacrifice again, a part of the repayment of humanity’s debt to the Teteo the divine. Accompanied now only by his calixque, he walked to a small temple on the outskirts of Chalco set aside for this ceremony. Its an interesting detail as there was the Templo Mayor as well as Temple of Tezcatlipoca but they went to a specific temple near Chalco.
It is not clear if his wives were Sacrificed as well there is not many sources talking about what happened to them and they were only around during the last 20 days of Tezcatlipoca's Ixiptla before he was sacrificed and if they had kids it wouldn't be uncommon to see an Aztec widow, if they were sacrificed as well that ends that question but it is simply not known what happens to them but since it was only the last 20 days it is likely they returned to normal life.
Alfredo Lopez Austin wrote “It was not men who died, but gods.” The death was necessary for their life, and thus for the whole of humanity. This metamorphosis was central to Nahua cosmology and to Tezcatlipoca himself wherein the universe was not static, but homeostatic, in constant movement. All of this was embodied, literally, in the single year in the life of a single man.