Ian Jansen is an Alchemist, about 18 years old. He had a crush on Sydney Sage. He had seen the Moroi who tried to kill Vasilisa Dragomir. When Sydney asked him he told Rose that he had seen a Moroi woman with him at there headquarters. It was because of his description that Rose came to know who was the killer of the Queen.
Sydney convinced Ian to give her a tour of the Alchemist library, so that she could break into the files and find out if the Alchemists were linked to the Warriors of Light.
At the end of Silver Shadows, Ian appears with Jared and Zoe Sage at Moroi Court in an attempt to get Sydney back into re-education. It is seen that his feelings for Sydney have now shifted onto Zoe, and that he is disgusted by Sydney's marriage to Adrian Ivashkov, a Moroi.