Gustaf

How Gustaf joined the Tourney
Gustaf 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.

While fighting Diane, Helbram used his ability to call upon Gustaf and asked if he could borrow his powers, to which Gustaf willingly agreed. Gustaf'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 Gustaf 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, Gustaf 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, Gustaf 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 Gustaf 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, Gustaf 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. Gustaf 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 Gustaf 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, Gustaf searches for Jericho, hoping she was safe. But unfortunately, Gustaf 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 Gustaf, 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, Gustaf, 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, Gustaf 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, Gustaf 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, Gustaf 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, Gustaf 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.

Preparing to make amends for his misguidings, Gustaf offers a friendly challenge to Yukimura and Nobuyuki Sanada's father, Masayuki.

When highlighted
Gustaf holds an ice shard in his left hand.

After the announcer calls his name
Gustaf shoots four ice shards as the camera zooms then says "Yes, of course."

Hail Bullet (Neutral)
After performing a hand sign, numerous jagged icicles form around Gustaf. The icicles are hailed upon the target to pierce and wound them.

Deadly Tundra (Side)
Gustaf swings his left hand then an icy wind flies at the opponent to freeze him/her for six seconds.

Cold Blade (Up)
Gustaf jumps into the air swinging his hands up and surrounding himself with five ice blades.

Ice Kill (Down)
Gustaf swings his hands down then icicles drop onto the opponent.

Killer Iceburg (Hyper Smash)
Gustaf creates a number of large icebergs and launches them at the enemy in a devastating barrage.

Blizzard Axel (Final Smash)
Gustaf forms a massive blizzard to rapidly damage his opponent and also slow them down for fifty seconds.

Victory Animations

 * 1) Gustaf forms an ice sculpture of a knight and says "Have the New Generation turned into monsters?"
 * 2) Gustaf makes five ice shards and sends them flying then touches the ground, bursting an icicle and says "Strength is not the only thing that wins in the end."
 * 3) Gustaf pushes his hand and makes an ice sword then swings it saying "A frostbiting conclusion."

On-Screen Appearance
Gustaf bursts through an iceburg and says "This can't be real... It looks like some kinda nightmare!"

Trivia

 * Gustaf's rival is Nobuyuki and Yukimura Sanada's father, Masayuki.
 * Gustaf shares his English voice actor with Malladus.
 * Gustaf shares his Japanese voice actor with Saitama.
 * Gustaf shares his French voice actor with Hien, Darkhammer, Gliscor and Arslan.
 * Gustaf shares his Arabic voice actor with Feraligatr, Robert Garcia, Takashi Kamiyama, Elfman Strauss, Hans Kleif, Haunter, Gai Tendo, Shizuma Kusanagi, Yellow Turbo, Fire Chief Michael O'Halloran, Uryu Ishida, Shinon, Hiei, Chen Gong, Jacky Bryant and Tapion.
 * Gustaf shares his Mandarin Chinese voice actor with Moriya Minakata, Beautiful Suzuka, Zombieman, Master Caesar Clown, Emperor Leo, Dino Mammoth, Rikuo and Sylux.