The first time we see Callisto is when she first goes after Xena. Callisto attacks villages and kills a lot of people, calling herself Xena. Of course Xena confronts the person making her name a symbol of hatred again. Finally after an impressive fight scene, Xena captures Callisto and takes her to jail. Meanwhile, a mob of people decided they would kill her themselves. Xena goes after them and stops Callisto from dying.
After Callisto's army has pretty much disappeared with Xena's help, Callisto was sent to what was, at the time, a maximum security prison. Naturally she escaped, and in a very fashinable way too. She freed her fellow prisoners and a new army was forming. Meanwhile, Gabrielle has met up with her ex-finace, Perdicus, now a less-boring man than the first time he proposed. This time she accepts, and marry's him. Callisto discovers the bard is travelling without Xena and decides to use her to break Xena down. Callisto attacked Gabrielle and Perdicus, Xena showed up just in time to save Gabrielle, but not in time to save Gabrielle's husband.
Gabrielle wanted revenge, so she saught Callisto. Gabrielle's good heart got the better of her, so instead of taking her revenge, she was captured by Callisto, and as expected, used as bait for Xena. Joxer, as usual becomes the distraction rather than the hero, Xena free's herself and chases Callisto. They race along the beach in greek style, chariots. Finally they crash and both fall into a pitt of quicksand. Xena uses her chakrum and whip to pull herself out, but let's Callisto sink.
Xena's continuing nightmares get worse. The guilt of killing Callisto taking over. Through this very guilt, Callisto get's to Xena through the dreams, and switches bodies with her. Xena becoming stuck in Tartarus as Callisto, and Callisto alive and kicking in Xena's body. Xena finally convinced Hades who she was and he gave her one day in the world of the living, after that, one of them had to go back to Tartarus. It doesnt take to long for Gabrielle to discover which is which warrior, and as usual, Xena wins and Callisto is sent back to Tartarus, only still in Xena's body.
Xena (in Callisto's body) finds Ares has lost his sword and godhood. In this episode (ten little warlords) Hudson does a wonderful performance as Xena. Xena agrees to help Ares if he switches her body back. So when his sword is retrieved, both women got returned to their respective bodies.
Hera is widely known for her hatred for Hercules, Zeus' son. So she saw Callisto as the perfect assasinator. Hera appeared to Callisto in the underworld and made her a deal. If Callisto killed Hercules, in the process she would get fruit from the tree of life making her completely alive, and...immortal. Naturally Callisto accepted, and Hera helped her escape the underworld, but she was still dead.
It was Hercules' birthday, so all his family were planning a surprise party, but when Hercules arrived he didn't find party hats, he found his entire family, almost dead, and Callisto sitting among them with a big grin on her face. She informed him that she had poisoned them, and the only cure was the apples from the tree of life. If he took her there, then he could get the cure.
So Hercules led her to the tree, of course the great Hercules wasnt going to let her become immortal, so he fourght her off and set the tree on fire, not before two apples fell to the ground. Callisto and Hercules fourght, and Callisto gave herself just enough time to eat a bit of one of the apples, she became immortal. In the battle that followed Hercules trapped Callisto in the underground tunnel they were in and escaped with the remaining apple. Hera was not happy about her tree being ruined, and so left Callisto there to rot for eternity.
Meanwhile, Xena was having some troubles. Gabrielle got an amazon by the name of Velasca very very angry. Velasca found some ambrosia, and pouf, she was a goddess and wanted Gabrielle's head on a stick. Xena knew the only way to fight an immortal, was with an immortal, so she freed Callisto. Callisto's incentive to help them was some ambrosia of her own, although both of them were planning to double cross each other.
Eventually Callisto and Velasca were battling it out on a bridge above a lava pitt, and Gabrielle had the pouch filled with ambrosia. Callisto got it off her and consumed its contents, in her own words "here comes trouble". Xena devised a clever plan which sent Callisto and Velasca into the lava pitt to be trapped forever.
We all know you can't keep Callisto down. Everyone has heard of Hope, the daughter of Dahak and Gabrielle, and the carrier of ultimate evil. She needed a partner, Callisto was it, so she freed her from the lava pitt. Together they plotted to kill Xena's son, Solan. They were succesful, Hope weaseled her way back into Gabrielle's life and used this advantage to kill Xena's son. Xena was obviously very angry. She and Gabrielle fourght. Gab poisoned Hope. Meanwhile, Xena and Ephiny battled Callisto and once again trapped her, this time in a cave behind a whole lotta rocks.
So History repeats itself, she gets out. Hope's ashes after being cremated regrouped to form one very scarred child. She got Callisto out and made her a deal. If she went back in time to Kill Hercules' mother before she had her son, then Hope would let Callisto go back to Cirra and save her family before her life turned to shambles. Callisto couldn't resist, it's what she always wanted, to save her family, and herself. First she teamed with Ares to trap Hercules in the alternate world so he would be out of the way and unable to stop her, unfortunately, whens he double-crossed Ares, he double-crossed her and told Iolaus what was going on. He allowed Iolaus to be able to follow Callisto wherever she goes, and come back to the present.
A lot of stuff happens, Callisto kills Herk's ma, but Iolaus goes back and fixes it, then they go to Cirrah, but thinking it was a bandit behind her Callisto accidently stabs her father, and when her mother attacked her she had no choice but to kill her. She sat with her fainted child-self, ready for them both to die. Until Iolaus came in and saved Callisto as a child. The older Callisto disappears for a little while here.
We see her again protecting Hope, now older and re-gaining her power in a coccoon. Xena shows up when they find out about Hope. Ares shows up too, he's on Hope's side and protects her. Hope 'hatches'. She's now fully grown. Hope and Ares get a bit friendly, and Callisto was not a happy goddess.
She swithced sides. She went to Xena. She agreed to help kill Hope in return for Xena killing her with the hind's blood dagger. Callisto wanted oblivion, no more life, no more tartarus, nothing. Xena agreed.
A lot went on. In the end Gabrielle killed Hope. The only thing was in the process, Gabrielle sent herself into the lava pitt too.
"Seeing poor dear Gabrielle sacrifice herself gives me a reason..for living", Xena stabbed her.
"No more living for you"
Callisto didn't get oblivion. She get's sent to what seems to be the christian hell. There she get's the chance to go back to earth. She takes on Caesar as a friend and get's a new haircut. Callisto is now pretty much industructable. Between the Romans and Callisto, Xena and Gabrielle get crucified and die. They end up on the other side too, seems they are to be angels. Except Callisto (now a yuck looking demon working for the devil) grabs Gabrielle and pulls her into hell.
Xena get's up to heaven and is determined to stop Gabrielle from eating the food which would turn her into a demon. Xena goes through a purification process and becomes an ark angel. The angels fly down towards hell. The angels tell Xena that if Gabby isn't a full demon, they can save her, otherwise there's only one other way. If Xena were to take on a demon's guilt and pain, they would be free and she would be stuck in hell forever.
The angels save Gabriellle. Xena fights it out with Callisto. When Xena has Callisto pinned Cally says "I will never stop hating you, you killed my family! I will hate you forever", then Xena says "No, you won't". To make up for her wrongs to Callisto, Xena takes on her pain. Callisto becomes the person she would have been if her family hadn't been killed. She even made her peace with Gabrielle.
After some more battling between the angels and demons, Xena and Gabrielle come back to live. Callisto is the one to bring them back, through Eli. She know's it's her time to be reincarnated, and chooses Xena to be her mother. Callisto touches Xena and she becomes pregnant. Callisto is then reunited with her family. She also helps Xena and Eli later on by realising their true paths.
The rest of Callisto's story, is under two other names, Livia, and Eve.