Gustaf

is a Holy Knight who serves under Helbram and Jericho's older brother.

Appearance
Gustav has short hair and is dressed in a regal Holy Knight attire.

Personality
Though not much is known of Gustav's personality, he is shown to be loyal to Helbram (until when Helbram revealed his intention to kill humans); as he aided his superior by offering his powers to Helbram's Link. Gustav appears to have no confidence on his sister in becoming a Holy Knight like himself. Despite that, he shows concern of his sister's safety.

History
Gustav argued with his younger sister Jericho that she'll never become a Holy Knight like him when she tells him of her dream of becoming one.

Kingdom Infiltration arc
While fighting Diane, Helbram used his ability to call upon Gustav and asked if he could borrow his powers, to which Gustav willingly agreed. Gustav's assistance was short-lived, however, as he was taken out after Helbram used place-switching magic to avoid taking a direct hit from one of Diane's powerful techniques, leaving Gustav to take the full impact of the blow. He is later seen to be perfectly fine,with no sign of injury whatsoever. When King asked Helbram whether he still intends to kill humans, Gustav and his comrades were shocked of their superior's true nature and as when the Cardinal ordered his subordinates to give all their powers to him, Gustav and the others tried to break their connection to Link, only to be taken control by Helbram's Blind Follow and gave all their powers to the mad fairy to battle the Grizzly's Sin of Sloth.

After an intense fight between fairies, Helbram's defeat broke the Link orb which freed Gustav and his fellow Holy Knights from his control although they were knocked unconscious when the Link orb's power feedback pushed them back hard. Once woken up, Gustav found himself in the ruined castle that him and his fellow Holy Knights were once in much to his shock and tries to wake his comrades up. Gustav remembered Helbram forcing them to use their powers through Link and hurtful words towards his sister, but was shocked to see the Liones capital being attacked by Demon like creatures and the Holy Knights were getting slaughtered, which Gustav called it was like Hell.

After relaying orders to assist their comrades fend off the Demon hybrids and evacuate the citizens to the Holy Knights who survived the castle attack, Gustav searches for Jericho, hoping she was safe. But unfortunately, Gustav was apparently crushed to death by his own sister's Demon form, leaving her inner self desperately plead anyone to stop her while her darker side gloated in triumph, holding her brother's body like a trophy. As Jericho was about to devour Gustav, the latter was saved by Gilthunder who recently recovered from Hendrickson's Acid and pleaded for someone to save his sister which Ban from the Seven Deadly Sins did by removing the strange "plant" inside of her which transform her back to normal.

Although still injured from the ordeal, Gustav, assisted by his fellow comrade, joins the Holy Knights surrounding Merlin's old castle to bar Hendrickson's escape while the Sins dealt with him. After the Sins were defeated by Hendrickson, Gustav and the rest of the Holy Knights attacked everything they got as he used his Ice Fang power as revenge for his sister but soon fell to fatigue of his wounds.

Later on, when Elizabeth awakened her powers after Hawk's death, Gustav was healed along with everyone else in the kingdom. He was given the plan of attacking both Meliodas and Hendrickson in order for the former to build up his ultimate technique: Revenge Counter.

Witnessing Hendrickson's defeat, Gustav and his comrades saw Meliodas fall from the sky who immediately got back on his feet but collapsed immediately afterwards. Seeing King Baltra Liones appear with Merlin, Gustav and all the Holy Knights bent their knees before their king in shame of their atrocities towards the people of the kingdom and blindly following Hendrickson and his evil plot all in the name of the Holy War, demanding heavy punishment for their sins only for the king to tell them to instead dedicate their power and efforts to restore the kingdom and prevent the same mistake from happening to avert the Holy War.

Abilities/Equipment
Gustav's strength is unknown, but as a Holy Knight it can be assumed he is quite powerful in his own right. Gustav has shown great endurance as he survived a Link force feedback and his sister's crushing grip, which would have been considered fatal. He even continued throwing his Ice Fang power attacks even in his injured state.

Abilities

 * A power that allows Gustav to form and manipulate ice.

Jericho
Jericho and Gustav are siblings although they are not on good terms. This is because in the past when she told him of her ambition to become a Holy Knight like him, he told her to give up and to stop embarrassing him. However, in Gustav dream state, it was hinted that the reason he said that is because he was worried about her and actually cares for her as despite Jericho transform into a Demon, Gustav begged for someone to save her and not kill her. In the Holy Knights' battle against Hendrickson, Gustav fought against his former superior in vengeance for his sister.