FTP, name this character from a Gottfried von Strassburg poem, the ill-fated lover of Tristan.
Her companion Brangene replaces her in a wedding bed, and she nearly has Brangere killed to keep the secret.  After she gives her lover a ring as a token of fidelity, he marries another woman with her name, known by the sobriquet "of the white hands."  Her uncle Duke Morolt was slain by her lover after demanding that Cornwall pay tribute to Ireland.  While traveling to Cornwall to marry King Mark, she and Mark's knight drink a love potion that works really well.  FTP, name this character from a Gottfried von Strassburg poem, the ill-fated lover of Tristan.
Her companion Brangene replaces her in a wedding bed, and she nearly has Brangere killed to keep the secret.  
Iseult or Isolde