<P> The group arrives at the lair of the Stygian Witches and learn that to kill the Kraken, they must obtain and use the head of Medusa, a gorgon who resides in a temple in the Underworld . Any living creature that looks on Medusa's eyes will turn into stone . Perseus, Io, Solon, Draco, and their remaining men heading into the Underworld . The men enter Medusa's temple lair while Io, being a woman and forbidden from entering, remains outside . Medusa kills most of the band, but Perseus finally manages to behead her by using his reflective shield to see her with his back turned . As he leaves the temple, Calibos appears behind Io and fatally stabs her . As Perseus and Calibos fight, Perseus accepts that he is a son of Zeus, picks up the Olympian sword, and stabs Calibos through the chest, which has restored him to his human form . With his last breath, Calibos urges Perseus not to become a god . As Io lies dying, she urges Perseus to leave her and save Andromeda and Argos . Perseus lovingly stays with her until her last breath instead of leaving immediately . Pegasus soon takes Perseus back to the city of Argos as the Kraken is released . The people of Argos seize and bind Andromeda to sacrifice her to the Kraken . Meanwhile, Hades reveals he does not require the faith or worship of mortals as Zeus does, as he has learned to survive on their fear . Hades then subdues the weakened Zeus . </P> <P> Perseus arrives at Argos and exposes Medusa's head to the Kraken, which makes eye contact just before it is able to reach Andromeda . The Kraken gradually petrifies and crumbles . Prokopion, the insane leader of the Cult of Hades, attempts to kill Perseus, but Cepheus stops him and is stabbed, before both are killed when the Kraken's petrified hand falls on them . Hades appears, intending to kill Perseus, but Perseus, invoking Zeus, throws his sword at Hades, forcing him back to the Underworld . Perseus rescues Andromeda, who is now crowned as Queen of Argos . She asks Perseus to stay by her side as King, but he declines . Perseus also refuses another offer of godhood from Zeus, who then proclaims that if Perseus is to live as a human, he should not be alone, and subsequently revives Io, reuniting Perseus with his one and only true love . </P> <Ul> <Li> Sam Worthington as Perseus </Li> <Li> Liam Neeson as Zeus </Li> <Li> Ralph Fiennes as Hades </Li> <Li> Gemma Arterton as Io </Li> <Li> Jason Flemyng as King Acrisius \ Calibos </Li> <Li> Alexa Davalos as Princess Andromeda </Li> <Li> Mads Mikkelsen as Draco </Li> <Li> Liam Cunningham as Solon </Li> <Li> Nicholas Hoult as Eusebios </Li> <Li> Hans Matheson as Ixas </Li> <Li> Rory McCann as Belo </Li> <Li> Luke Evans as Apollo </Li> <Li> Danny Huston as Poseidon </Li> <Li> Alexander Siddig as Hermes </Li> <Li> Agyness Deyn as Aphrodite </Li> <Li> Pete Postlethwaite as Spyros </Li> <Li> Elizabeth McGovern as Marmara </Li> <Li> Luke Treadaway as Prokopion </Li> <Li> Polly Walker as Cassiopeia </Li> <Li> Vincent Regan as Cepheus </Li> <Li> Kaya Scodelario as Peshet </Li> <Li> William Houston as Ammon </Li> <Li> Ian Whyte as Sheikh Sulieman </Li> </Ul> <Li> Sam Worthington as Perseus </Li>

Who played io in clash of the titans