"Advent! To the top."
Sieg's physical form.
- Height: 184cm
- Weight: 98kg
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Sieg (ジーク, Jīku?) is the Imagin who arrived 6 months prior to Ryotaro becoming Den-O, originally intending to forge a contract with a young wealthy woman named Shiori Takayama. But she was pregnant and Sieg ended up inside the baby in a deep sleep until he emerges in physical form with no memory of the wish and believes that he forged a contract with the baby instead of Shiori as he had planned. Sieg took his "brother" out of the strange area he found them in, only to meet Ryutaros who takes Sieg to the Den-Liner, where the Imagin got his own sleeping car with a lavish bed and Ryutaros helped fill it with stray puppies and kittens. Because of his princely mannerisms, Sieg becomes easily infuriated when treated with disrespect. Because he was "born" in 2007, Sieg possesses extraordinary unique abilities like making other Imagin shrink to four inches in height for a bit of time with the phrase "Kneel down to me!" (頭が高い!, Zu ga takai!?) and it appears that no other Imagin, including Ryutaros, can force him out of Ryotaro's body as Sieg needs no contract to possess humans. When possessing Ryotaro, Sieg says "Advent, above it all…" (降臨、満を持して…, Kōrin, man o jishite…?). Because Yusuke's mind is too young to maintain Sieg's existence, he begins to fade away, but not before becoming Den-O Wing Form to fight the Scorpion Imagin. After the Scorpion Imagin is defeated, Ryotaro returns with a Rider Ticket that he got from Shiori that bore the date June 1, 1997, revealing that Sieg did have a contract with her. He then remembers Shiori's wish for her baby to be born safely, fulfilling that contract. With the Den-Liner gang's help, Sieg arrives in the past to live peacefully. However, during the hijack of the Den-Liner, Sieg offers his aid to Ryotaro in the Tarōs' stead as only he could possess Ryotaro's body, deciding to repay his debt to Ryotaro for preventing his disappearance. He battled the Cobra Imagin in the Edo period while befriending Kotaro. He would aid the Den-Liner gang two more times, aiding in Ryotaro getting stronger and later to assist Ryotaro and the others in defeating Kai's army of Imagin after being retrieved by Naomi. But due to his birth and time with Ryotaro creating a time lag, Sieg is able to maintain his existence as he takes leave in the Den-Liner. During the events of "Final Countdown", Sieg greets the Den-Liner crew in May 23, 1729 as their contact, offering his help as Wing Form during the epic battle against the revived Imagin. Following a pattern of showing up when help is needed, he appears later to help in the battle of the returning Oni forces.
During his first time on the Den-Liner, he demanded that the others call him "Prince" (プリンス, Purinsu?) and asked for Hana to be his "Princess" (姫, Hime?), and was punched for each time he called her that. After his return, Sieg refers to the Tarōs as his "family" instead of his "friend" phrasing. In the Imagin Anime OVA, Sieg had an additional power "Super-Ultra Kneel down to me!" (スーパーウルトラ頭が高い!, Supā-Urutora Zu ga takai!?) that allows him to shrink everything in sight, even an entire planet.
Sieg is based on the swan in the ballet Swan Lake (白鳥の湖, Hakuchō no Mizūmi?) and named after its Prince Siegfried (ジークフリート王子, Jīkufurīto Ōji?) (the word "Swan" is written on his breastplate).[1] His name is given as "Zieg" in the series' photobook DETAIL OF HEROES: Masked Rider Den-O Exclusive Photograph Collection: IMAGINE (DETAIL OF HEROES 仮面ライダー電王特写写真集 IMAGINE, DETAIL OF HEROES Kamen Raidā Den'ō Toku Utsushi Shashinshū: Imajin?), however, other materials give his name as "Sieg," such as the earlier photobook Masked Rider Den-O Photobook: IMAGIN (仮面ライダー電王フォトブック IMAGIN, Kamen Raidā Den'ō Fotobukku Imajin?).