Julius Amidonia, later renamed as Julius Lastania (ユリウス・ラスタニア), is the exiled, unofficial ruler of Amidonia before its annex. He is the son of the late Gaius Amidonia and older brother of Roroa Amidonia. Later on, he marries into the Royal Family of Lastania and adopts their surname.

Julius was a vain, egotistical individual, and had dreams of grandeur and conquest. Though not as hot-headed as his father, he did share the same ideals. However, his ability to govern a country was severely lacking as he did not understand the needs of the Amidonian citizens, nor was he able to solve domestic issues, since like his father, he followed a 'military first' outlook.

His personality becomes a bit more subdued after the disastrous invasion of Elfrieden and the annexation of his country. He initially held a large grudge against Kazuya for his defeat, and against his sister for taking away his country and birthright.

However, due to leading the forces of the Kingdom of Lastania and his relationship with Tia Lastania, his attitude has changed for the better. He now supports his sister's engagement to Souma and even presses his sister into having a heir soon to continue the Amidonian bloodline.

(Source: How a Realist Hero Rebuilt the Kingdom Wiki)