Sergiad

Duke Sergiad Cowen ("High Lord Sergiatte Cowen" in Crunchyroll's subs) is the head of the Cowen clan, ruler of Maihama, and the chairperson of the Eastal League of Free Cities.

He had two daughters, Langrissa and Saraliya, with his late wife. While Langrissa chose not to marry or have children, Saraliya later married Phenel and bore three children : Risselthea, Raynesia, and Iselus.

Appearance
He has a somewhat old, wizened appearance with completely white hair, with both a beard and a mustache. Like his granddaughter Raynesia, he has blue eyes. He is always seen wearing his crown.

Personality
Outwardly, he has a commanding presence and is treated with the utmost respect by his fellow nobles. Inwardly, he is open-minded and sees the Adventurers more as equals rather than as potential members of the League unlike other nobles. He later decides not offer them membership and instead signs a treaty of non-aggression and basic trade between them.

Despite being an NPC with a Western-themed lifestyle, Sergiad has a penchant for Japanese cuisine where his favorite food are dorayaki and wakame. Before going to sleep, he apparently has a need to drink a warm glass of milk.

Round Table Alliance arc
As the Round Table Alliance was formed and things within the city stabilized, the news of its formation spread throughout the land and new revolutions and discoveries were being made everyday. Duke Sergiad heard of this information and sent out spies in order to check things out and report back to him in order to discover what the Adventurers intentions were.

Summer Training arc
The Duke sent out an emissary envoy in order to invite the leaders of the Round Table to their annual conference of the lords in order to establish better relations with them, even offering them nobility titles. Later he met with them personally at the start of conference, he sat with them and conversed with them about several subjects most notably with Krusty in order to get a better understanding of them, he did not seem as much as worried as the other Earthlings that were there and even advised them to relax and enjoy themselves.

Libra Festival arc
While he was satisfied that the crisis with the Goblin armies was resolved and relations with the city of Akiba and the Round Table Alliance had been established, he was still disappointed by his granddaughter's brash actions to enlist the help of the adventurers. In order to make up for it, he sent her to be the official ambassador of the People of the Earth and the League of Freedom Eastals in Akiba.

Noosphere arc
Duke Cowen and Isaac have been having weekly meetings with each other since Isaac was placed in Maihama to train their knights and have become quite friendly with one another. The duke asks Isaac to take his grandson Iselus in under his tutelage and to keep him safe as he plans on appointing the boy as the heir to the Maihama duchy and thus the leadership of Eastal during his birthday party, despite the boy being only 8 years old. Moreover, he knows of the danger of war with the Holy Empire Westelande and fears for the boy's life. Isaac agrees both to take care of Iselus and to train him

The night of Iselus' birthday party, Isaac and Calasin thwart an assassination attempt on Iselus by People of the Earth assassins from Westelande. Unfortunately, this is also the first night of the Eternal Moth invasion, and Serjiad falls victim to their scales and enters a deep sleep, his MP being continually drained. Serjiad would not wake up until the conclusion of the Shibuya Raid, where Shiroe and his companions destroy Taliktan, the mastermind behind the Eternal Moth invasion.

Collapse of the Round Table arc
He was sitting with Saraliya when Raynessia defended her choice to stay in Akiba and refused her arranged marriage.