As Terra Nostra shifts between the eve of the new millennium in 1999 and the first and sixteenth centuries, the thirst for power presents itself as a recurring theme. As Tiberius and Agrippa clash, as the conquistadors ravage the Americas, and as Philip II stands aloof building El Escorial, Fuentes shows that the history of the Spanish-speaking world is one of bloody conquest and despotic rule. This sweeping view across space and time, and the use of the new millennium as a framing device, lends the focus on power a grand and universal feeling, while the primary story, set in sixteenth-century Spain, gives the novel a sense of specificity, as Fuentes explores the history of Spain and its powerful colonial empire.

In the novel, Spain is indisputably an empire that has fallen from its former might, and Fuentes suggests that the root of this lies in the nation's inability to adapt to a changing world. The in-depth exploration of Philip II's life and obsessive orientation toward religion and El Escorial, paired with his refusal to recognize the significance of the so-called "New World," fill out this picture. Spain clings to old ways and to religion, isolating itself from the world, and the world inevitably changes around it. Former Spanish colonies are framed as having historic ties to Spain but being able to grow and change in ways that defy the old empire. In the closing scenes of the new millennium, we see the embrace of change as a wonderful and magical experience, as the story offers hope for the world's direction to tend toward greater equality and acceptance.

Through the comparison between Philip II on one hand and Isabel, Pollo, and Celestina on the other, strong contrasts are drawn between asceticism and pleasure. Fuentes clearly aligns Philip II's asceticism with the king's desire for power and control, but the author's orientation toward the hedonistic tendencies he contrasts this with are slightly less clear. At least in part, however, Fuentes aligns the liberation of desire with greater equality and the blurring of lines of difference, which can be seen especially clearly in the union of Pollo and Celestina as symbolic of gender equality and liberation.