The Invincible Archmage — Episode 6

After the Magic Emperor is assassinated, his son Edward hides as a servant for 20 years, mastering star magic. When his benefactor is forced to marry an orc chief, Edward reveals his power to save her and is found as the lost heir. He wins the magic tournament, annihilates 100k invaders with a comet spell, saves his comrades, and becomes Emperor.