This page contains spoilers from the light novel! Read at your own risk.
Václav was a middle-aged man who had the silver eyes and long silver hair of a Celena. He wore a unique Prussian blue uniform of the Republic. Unlike the majority of the Republic officers uniforms, which had closed collars, his was open, showing his collared shirt and tie. His badge to denote his rank as well as a row of ribbons to signify his achievements as a military officer were also pinned on his uniform.
Unlike the majority of the Alba population in the Republic, he opposed the oppression against the Eighty-Six by the San Magnolian government. He was described as a kind man and a loving husband and father. While he wanted nothing more than to make the Republic a better place, he was also highly idealistic. This lead to him being ignorant and reckless, as he was willing to bring Lena to the battlefield so she could see the atrocities being committed against the Eighty-Six.
Later when he became a Shepherd for the Legion, most of his former personality seems to have been erased as he's become cold and calculative.
Václav was one of the few survivors of the Republic Armed Forces from before the first invasion of the Legion. He understood the violent and corrupted nature of the Republic when he witnessed the parents of a pair of siblings—presumably Kurena and her sister—being tortured to death. He opposed the oppression against Eighty-Six by the government of the Republic, but his voice was not significant enough.
Three years after the start of the first Legion invasion, he decided to show his daughter Lena the brutal oppression that was being executed by the Republic. They took a flight to the frontlines but were shot down by the Legion's anti-aircraft batteries. He died in the incident but his daughter survived. His head was not shown to be attached to his body.
Due to his experience being part of the Republic Armed Forces, and his rank as a colonel, it's implied that he was a strong and fully capable military leader.
He loved Lena very much, however he was unafraid to show her the crimes the Republic was committing to the Eighty-Six, as he was willing to bring her to the battlefield to see with her own eyes. He was also protective of her, having shielded her as their helicopter crashed under enemy fire. 
His teachings and views were carried on by Lena, even long after his passing.
While sharing different views in regards of the Eighty-Six, it had been shown that she still loved him when he died. His death had affected her greatly as she didn't wanted Lena to end up like him.
Karlstahl had been best friends with Václav and had known him for years. He fought alongside him nine years ago during the initial invasion of the Legion as part of the now demolished Republic Armed Forces.
Karlstahl himself described Václav as a kind man who's goal was to make the Republic a better place. He thought it was a shame to lose a man with a strong sense of justice from an enemy attack. However he also stated that Václav's ignorance and stupidity were the result of his death by being so reckless for the sake of his ideals. Furthermore, he pointed out that Václav didn't realize that all he did was watch the atrocities of the persecution of the Eighty-Six, just like the rest of the Republic. He continued to criticize Václav for being all talk about equality while he did nothing to truly change their situation. He correctly discerned that Václav subconsciously felt that only the Eighty-Six could die on the battlefield, and the fact he took Lena on the battlefield proved that.
"'We are going to the battlefield, to see it with our own eyes'" ― To Vladilena Milizé as they embark to the Eighty-sixth district
- Václav Milizé is currently the only known high-ranked officer of the San Magnolia military who has been converted into a Legion.
- At the time of his demise, he held the rank of Colonel, a rank that was eventually obtained by his daughter as well.
- Prior to the fall of the Gran Mur, Václav is known to be the last person of the Republic military to be officially listed as killed in action by the Legion as processors aren't technically human, based on the racial discrimination laws by the Alba population as well as Alba who fought alongside with the Eighty-Six, aren't recognized either as KIA.