Throughout City of Glass, the characters all grapple with their relationship to power—whether magic or otherwise—and its ability to both strengthen and corrupt. Clare uses the absolutist law of the Clave, Clary’s unique gift to create powerful runes, and Valentine’s villainous character arc to explore the complexity of power and the ways attempts to restrict it contribute to its use or abuse. Clare suggests that restrictions placed on power to ensure ethical and equitable treatment for all allow for the healthy use and expansion of power, whereas restrictions intended to preserve the power of a privileged few through the marginalization and oppression of others lead to disaster and destruction.

As a global community, the Shadowhunters are divided ideologically on both a geographic and generational level. As the governing body of the Shadowhunter world, the Clave oversees Shadowhunter law and deals with any transgressions against its rules. Since Shadowhunters were created, they have lived by a strict code that dictates how all Shadowhunters fight, socialize, and govern themselves. Those who live in Idris, surrounded only by other Shadowhunters, tend to be more conservative than those who live at Institutes around the world—integrated with mundane and downworlder society—a diversity of community that balances the Clave’s absolutist power structure.