Noun
zealot - A fanatical person who is unyielding in their spiritual or political pursuits.
Juliet went into the hills alone to seek God, even though her friends called her a crazy zealot. She later testified that speaking to God in the storm was a profoundly healing experience.
Lust - A powerful urge or longing – a deep-seated drive that can sometimes lead to irrational or impulsive behavior, often of a sexual nature.

He liked reading the old story about the prince who had a lust for power that drove him to betray even his closest allies.