Siebold is a Master Water-type Trainer and member of the Kalos Elite Four. He specializes in Type Pokémon. He is also a very gifted chef. In the Battle Chateau, he is known as a Duke, one of the highest of ranks overall.
Siebold is very tall and slender, with pale white skin. He has light flaxen hair that curls around his head in graceful ripples. He possesses penetrating catlike eyes that are a deep sapphire-blue colour. Siebold wears a very regal uniform; his cloak-like garments are mostly pure white, mixed with some blue patterns, similar to a garment worn by royalty. The front of his shirt resembles a chef's garb, with four large white buttons, but it is merged with medieval-looking apron-like vestments, and is also slightly reminiscent to the uniform of a sailor. His uniform is high-collared, and his collar is rippled around the edges, like a scallop shell, and coloured blue and white,. He wears a unique cerulean blue striped cravat (a flowing, wispy tie) with a deep blue teardrop-shaped jewel pendant hanging round his neck. His shoes are white with blue trim.
Siebold views Pokémon battles as an art, comparable to a chef preparing cuisine food. Often seen frowning, Siebold is a solitary, standoffish, and very contemplative, intelligent, and wise person. He is also extremely passionate about his battling skills, which he considers an art form. Despite his calm appearance, Siebold is moody and has a very hot temper. He becomes extremely frustrated with trainers who fail to view Pokémon battles as a form of art, even going so far as to shouting at them and calling them "foolish children".