The quick version of what happen to the Classic period “ahau” concept of governmentality is that it is exactly that what collapsed during the so-called Maya collapse. As you probably are aware, the “K’uhul ahau” (or holy kings) were the semi-divine rulers of classic period cities, especially around the Peten area. We know about them because this is exactly what it was depicted in the hieroglyphs, their pedigrees and actions as they related to issues of power. Specifically, the glyphs known as the “emblem glyph” are the ones that label a person as the K’uhul ahau (holy king) of a particular city. However, by the 7th to 8th century, we see a proliferation of claims to power; it is almost as if there were many elites claiming hereditary rulership. Because the Maya politico-economic structure required elites to harness vast amounts of resources for various activities in order to legitimize power, the increase in elites generated high-stress environmental conditions. Coinciding with this stress were other social factors like shifting trade networks and increase in warfare. Thus, by the end of the 8th century, the ever-growing elites were unable to deliver on their social promises causing people to loss faith in the K’uhul ahau system. Commoners, artisans, and others apparently abandoned their homes and cities in the Peten in order to find better economic opportunities elsewhere in the Maya area, especially in the Yucatan Peninsula, leading to a significant depopulation, even abandonment of major cities like Tikal, Calakmul, Copan, and Palenque. The new thriving sites of the Yucatan area like Chichen Itza, Kuluba, and Xuenkal, and perhaps even Uxmal did have rulers, but they were not as powerful as their predecessors. In fact, by this time Mayas stopped using hieroglyphic inscriptions to depict their rulers. For example, at Chichen Itza, the only full glyphs that we have come from the Initial series group.

Now, as far as the Halach Unik or Halach Unic, the colonial sources tall us that they were the preconquest (Postclassic period) officers said to have been senior to the batab (the local village chief). So a Halach uinic was the local village chief (a batab) of an important Cah (the indigenous geopolitical structure) that had achieved dominance over a region. In other words, Halach Uinic was an honorary term for an especially powerful ruler in a specific region. So, while a Halach Unic was a pominent individual, it did not have the same power as a K’uhul ahau. If you want to learn more about rulership during Late-Postclassic/ Colonial Maya communities, I really recommend you reading Mathew Restall’s The Maya World: Yucatec Culture and Society, 1550-1850.