Fate/Zero, Magi: The Labyrinth of Magic Recommendations
Both anime contains candidate for a king. Powerful sidekicks that will guide and help them
Both are about a battle enveloping the world showcasing various ideologies and how they clash.They are also similar in the way that heroes/kings join forces with powerful magic beings in order to shape the world in their favor.
Both shows feature similar brilliant plots and turn the journey of multiple main characters into a great story.