Code Geass basically has the same plot as Baldur's Gate and Baldur's Gate II: Throne of Bhaal.
1. Extremely powerful, god-like father who seeks immortality and killing other gods.
2. Tons of children who are destined to fight each other, believing they'll inherit their father's throne, but it's all just a setup.
3. Tons of parallels with Norse/Pagan mythologies, legends and folklore.
4. One unremarkable son stands out from the rest early on, killing several of his siblings violently, raising an army and becoming quite popular with the nobility.
5. That son wears grisly black armour.
6. Son is defeated by his half-brother,at he ruins of an old temple away from the main battle field.
7. Son returns after a year to restart his war of conquest.
8. The archvillain of the story is actually not the father, but a young and beautiful priestess who appears to assist the children, actually driving them against one another.
9. At the end of the story, the black son and the priestess have a battle in a supernatural realm originally owned by the son's father.