The Servant's True Name is Captain Hendrik van der Decken (ヘンドリック・ファン・デル・デッケン船長, Hendorikku fan deru Dekken Kanchō?), captain of the infamous Flying Dutchman. He was cursed by a devil of the ocean. The curse is one to wander the seas forever, only being able to come on land once every seven years, and not being able to dock at the same place twice unless it has been so long that the place's name has changed and no one living there remembers him. He is searching for a wife.
The Captain has the appearance of a silent but strong sea-faring man with wild black hair and unshaven beard.
The Captain's personality seems to be stoic and quiet, but his shoulders did slump slightly when his Master brought up how he once again failed to find a wife and could try again when they dock in seven years. When summoning his Noble Phantasm he breaks his usual stalwart demeanor to bellow out a sea shanty while his ship appears.
Decken and his Master, Ahasuerus had made port at the Akihabara Ward of the Mosaic City. Hunted by Kundry who deems him her lover, Erice Utsumi escorts the Master-Servant pair to the docks for them to make their escape. Erice tries to befriend him over their shared status of both bearing curses, but Decken rebukes her. He chides Erice for being intoxicated by the idea of being a hero by killing evil-doers, and that while she thinks she is the master of her Dread Spirits, they in turn are using her. He warns her that some day she will call forth a great evil, and when that time comes that which she has clung to so dearly will instead force her to her knees.
Having made their way to the harbor, Decken summons his legendary ship, the Flying Dutchman, at the behest of Ahasuerus' Command Spells which promptly destroys Kundry's gremlins before leaving the city for good.
Due to a curse Decken is only able to dock at land once every seven years, and must spend those seven years at sea. However when he does come ashore Decken is able to dock anywhere in the world, even ports protected by powerful protective barriers.