Negative effect of power
The main theme of the novel is the theme of power given to certain people and how it affects them. The main effect of it is corruption and desire to control others. There are seemingly no Epics that are in the role of a hero, every single one of them is spoiled and merciless. At first, it seems as though they are choosing the path of destruction and fear, but we discover at the end that it comes a side effect of using their powers. Therefore, the novel presents an idea that the power corrupts people without their own choosing.
Among the examples from the novel are the Epics, human beings with unimaginable power. Most of them use this power to destroy and rule over others, but it ultimately just leads to nothing but chaos and death.
What Epics didn't understand, however, was that their power was the cause of their desire to destroy and kill. Simply not using their power at all would've made them normal human beings, as seen by Prof, (Reckoners leader), who had never wanted to use his power since it unwillingly made him arrogant and act horribly.
Revenge
David is seeking revenge for what happened to his father. He dedicated his entire life to that, it is what kept him going, what helped him survive and what made him join the Reckoners. Moreover, he questions his motives at times, after seeing that the Reckoners are set on following his plan and taking down Steelheart, but he knows, and Prof encourages him, that it is the right thing to do. Witnessing his father's death was disturbing, but it also shaped his character seeing his ordinary father heroically, without fear (which is the key to his revenge), stand up against those powerful beings.
