Known as tlamacazque, or "the givers of things," Nahua religious specialists energized Mexica (Aztec) imperial expansion through carefully crafted art, architecture, and ritual performances. As leaders, tlamacazque protected sacred forces, brought ritual art to life, and shaped ceremonial spaces to articulate Mexica presence across the Valley of Mexico and its environs. When Europeans invaded, their demonizing writings muddled the complex roles these specialists had. Although scholars now have a more complete picture of Nahua religion, we still know very little about the tlamacazque who stood at its heart, as well as the art and architecture they fashioned, used, and transformed. A study of tlamacazque art and architecture thus provides a unique window into the lives of these leaders that are otherwise lost to us in colonial texts. By exploring their material and spatial worlds, my dissertation is the first art historical study of tlamacazque from the height of the Mexica empire (A.D. 1325 – 1521) into the early years of Iberian occupation. By analyzing sixteenth-century Iberian and Nahua texts, surviving Mexica architecture such as religious schools and sacred platforms, and religious art such as ceramic censers, musical instruments, and incense and paper sculpture, my research will examine the practices these leaders undertook to shape Mexica state religion. In addition, I will investigate how these leaders, materials, and spaces adapted during the first years of Iberian occupation. To ground my understanding of Nahua culture and history, I will collaborate with modern Nahua religious specialists and community members in Chicontepec, Veracruz on this study of their past. By culling methods from art history, ethnohistory, Native American and Indigenous Studies, and the anthropology of religion, I will show that to understand Mexica and early colonial religious practices broadly, we must first understand the tlamacazque and their material and spatial worlds.