Together with her partner, Robert Westerholt, Den Adel formed Within Temptation (initially called The Portal, though the name was changed before their first recording) in 1996.
Bersama suaminya Robert Westerholt, den Adel membentuk Within Temptation (awalnya berdiri diberinama The Portal, meskipun nama ini diubah sebelum rekaman pertama mereka).