Dubhe Alpha Siegfried

Dubhe Alpha Siegfried (アルファ星ドゥベのジークフリート, Arufa-sei Duube no Jīkufurīto) is one of the seven God Warriors of Asgard. He serves as an antagonist during the Asgard Arc.

The Invicible Warrior
Siegfried is said to be the reincarnation of the legendary hero Siegfried, a famous warrior and grandson of Odin, who battled and defeated the dragon Fafnir. However, he fell victim to a cursed ring found among Fafnir's treasures, which ultimately lead to his death at the hands of the Valkyrie Brynhildr, whom he became betrothed to and later was manipulated into betraying. Angered by his infidelity and unaware that he had been influenced by others, Brynhildr convinced Siegfried's brother-in-law to murder him.

Reborn in the present time, Siegfried had met Hilda, the priestess of Odin, long before becoming a God Warrior. Although life was hard, Hilda ruled Asgard with kindness and benevolence, and prayed that war never come to Asgard. Siegfried loved Hilda secretly in his heart, and vowed to protect her with his life.

When the time for the return of the legendary God Warriors had come, Siegfried and his best friend Merak Beta Hägen were chosen to become God Warriors. However, he noticed that Hilda had changed, becoming more aggressive and power hungry soon after. He was additionally warned by Freya that a drastic change had come over the priestess of Asgard. Siegfried didn't belive Freya and, despite Hilda's altered personality, he remained loyal to her.

The Last Defender Of Asgard
After the six other God Warriors were defeated, Siegfried was the last opponent for Seiya in front of the statue of Odin. Siegfried stated that he is impressed with how far Seiya had come despite being badly damaged. Seiya tells Siegfried that Hilda was under the control of the Nibelungen Ring. But Siegfried does not believe it, and considers Seiya's words blasphemous. Seiya attacks him with his Pegasus Meteor Punch, but Siegfried deflects the attack as if his body was protected by an invisible shield. He then uses his Odin Sword attack to knock Seiya out.

Phoenix Ikki, Andromeda Shun and Cygnus Hyoga came to the statue of Odin, and were shocked to see that Seiya had been defeated. Ikki challenges Siegfried to fight, but is ultimately defeated in a similar manner. Then he turns to Shun and Hyoga, both wounded from previous battles, and defeats them both with Odin Sword, leaving the four Bronze Saints fallen.

To his surprise, Seiya gets up and tries to fight him again. Siegfried then prepares his deadliest attack, Dragon Bravest Blizzard, against Seiya, but Shaina, arriving with Shiryu in time, jumps to protect Seiya from the attack. Despite this, both were "defeated" by Siegfried's technique.

Shiryu, seeing his status as the last Bronze Saint standing, faces Siegfried in battle. However, all of his attacks, including his Rising Dragon Lord, were negated by the barrier created by Siegfried's Cosmo. Shiryu then realizes that his best shot at defeating Siegfried was to use the Proud Dragon Lord against the God Warrior. However, the spirit of Shura warns him, saying that using this technique would result in the death of both, and the destruction of the last Odin Sapphire. Detecting Shiryu's reluctance to use this attack, Siegfried is released, and attacks him with Dragon Bravest Blizzard.

Noticing the opening Siegfried leaves is similar to that of his own technique, Shiryu uses his Rising Dragon Lord on Siegfried's heart, causing him to grab at his chest groaning in pain. Shiryu then explains how when Siegfried killed the dragon Fafnir and bathed in blood, a leaf landed on his back, leaving his heart mortal and vulnerable. After Shiryu parts Siegfried's weakness to Seiya, the Pegasus Saint got up and challenged Siegfried again. Siegfried fights Seiya, causing the chest area of his God Robe to be strained.

Siegfried persists shortly after Siren Sorrento appeared, one of the Poseidon's Mariner Generals, who spoke as Polaris Hilda was changed by the Nibelungen Ring. Siegfried, full of anger, faces Sorrento and tries to kill them both by ascending into the sky, only for him to be terrified by an illusion Sorrento cast to weaken Siegfried, leaving him to die alone as the Mariner General survives.

Techniques
Odin Sword (オーディーン・ソード, Ōdīn Sōdo): Siegfried unleashes his Cosmo, firing a laser at his opponent's feet and then shooting them upwards to inflict additional damage from the debris.

Dragon Bravest Blizzard (ドラゴン・ブレーヴェスト・ブリザード, Doragon Burēvesuto Burizādo): The most powerful attack in Siegfried's arsenal. The Alpha God Warrior charges his fists, and then fires a cold blast of wind in the form of a two-headed dragon, freezing everything in his path. The one major drawback to this attack is that it forces Siegfried to expose his chest for a millionth of a second, which both Seiya and Shiryu took full advantage of.

Trivia

 * As stated prior, Siegfried's character is based on the tragic hero of Richard Wagner's Ring cycle. In the original Norse myth, his character is named Sigurd; Siegfried had originally been the name of Sigurd's father.
 * Siegfried's God Robe is meant to resemble Fafnir, a former dwarf prince who fell victim to a powerful curse that transformed him into a dragon.