Cirilla Fiona Elen Riannon (known as Ciri or the Lion Cub of Cintra), born in 1251, most likely during the Belleteyn holiday - a princess of Cintra, daughter of Pavetta and Duny (Urcheon of Erlenwald) and granddaughter of queen Calanthe.
After witcher Geralt lifted the curse from her father, he demanded from Duny what he had but didn't know he did (see: Law of Surprise), which turned out to be Ciri (as Pavetta was already pregnant with the child). Six years to the day after her birth, Geralt went back to Cintra for her, but did not take her with him to Kaer Morhen at that time. In fact, he didn't even lay eyes on her and only spoke with Calanthe, and the queen divulged no information to him, not even the child's gender.
While she was still an infant, Ciri's parents were both lost in a storm at sea and presumed dead. She spent her youth in Cintra and the Skellige Islands in the care of her grandmother. She first met Geralt when she was lost in the forest of Brokilon. She was nearly taken by the dryads and made one of them, but the queen of the dryads, Eithné unexpectedly let the girl choose her own future. Ciri chose Geralt and tried to stay with him after they left Brokilon, but the witcher would not take her with him. Instead, he left her with the druid Mousesack who was working for Calanthe. Then came the slaughter of Cintra.
During the Nilfgaardian invasion of Cintra, Ciri was kidnapped by a Nilfgaardian knight called Cahir Mawr Dyffryn aep Ceallach (though his identity was not known at the time), but she managed to escape and wandered aimlessly for some time through Sodden until she was ultimately adopted by a merchant's family.
Coincidentally, Geralt had been helped by that same merchant and transported to his home. So once again Ciri and Geralt were reunited. This time the witcher took her with him to Kaer Morhen, where under the supervision of Triss Merigold she underwent partial witcher training (but not the mutations) with Geralt, Vesemir, Lambert, Eskel and Coën. It was also there that it was confirmed that she was a source.
Geralt and Triss later took her to the Temple of Melitele in Ellander where she received instruction at first from Nenneke, and then from Yennefer, who began Ciri's magical training in earnest. As news of war began to spread, Ciri and Yennefer left Ellander for Gors Velen and ultimately Thanedd Island and Aretuza where the sorceress intended to enrol the girl as well as attend a conference of mages.
Things did not work out as planned though, not by a long shot. There was a coup during the conference and several individuals including Vilgefortz and Cahir tried to capture Ciri once again, and once again failed with the girl escaping through an unstable magical portal in Tor Lara. Because of the portal's nature, Ciri was simply ejected in mid-air over the Korath desert.
Unaware of where she was and without obvious recourse, the girl decided to make her way out of the wasteland by heading west. Unfortunately she wandered around in circles for some time before deciding to use the stars as a guide. She nearly died of exhaustion, dehydration and starvation. Luckily to her she met a unicorn whom she nicknamed Horsey that helped her out of the Frying Pan (a folk name for the deadly desert).
Ciri then joined the Rats band under the name Falka. Bounty hunter Leo Bonhart was hired by Stefan Skellen to kill Ciri and by baron Casadei to capture her alive. Bonhart killed the Rats and cut off their heads after their deaths. He neither killed Ciri, nor brought her to baron Casadei, therefore not fullfilling his contracts. Bonhart imprisoned her for some time, beating her, mistreating and forcing her to kill in the arena at Claremont, which belonged to his cousin Houvenaghel.
Ciri managed to escape with the help of Neratin Ceka when Bonhart had taken her to the village of Unicorn on the eve of the equinox. He had gone to meet with Skellen and Rience and possibly negotiate some terms to release Ciri. Bonhart then killed Neratin Ceka, and Skellen seriously wounded Ciri, disfiguring her with an orion as she fled the village on her mare, Kelpie.
Later, she was found, near death by Vysogota of Corvo, who hid and healed at his hermitage in the Pereplut swamp. She stayed with Vysogotha until shortly after Saovine when she set off to find the Swallow's tower.
Being a twin tower to Tor Lara, Tor Zireael had a portal which led Cirilla to the world of the Aen Elle elves. There she was greeted by Avallac'h, an Aen Saevherne. He explained to her that she had to 'pay the debt' referring to the perceived loss to the Aen Elle when Lara Dorren took Cregennan of Lod as her lover. The elves believed that the latter had 'stolen' Elder Blood from them by marrying Lara. To atone for that 'crime' Avallac'h wanted Ciri to beget a child with Auberon Muircetach, the king of the Aen Elle. That being the only way Avallac'h would let her return to her own world. On their way to Tir ná Lia, the Aen Elle capital, they met Eredin and his Dearg Ruadhri. Ciri was initially quite infatuated with him - he realised that and tried to use it to control her. They also came across a pack of unicorns which appeared to be at war with Aen Elle.
In Tir na Lia Ciri finally met Auberon, who many times tries to conceive a child with her, however he could not - to him she was just a human, a being of no interest for an Aen Elle. Nevertheless he was very proud and refused to admit it. Eredin suggested using a 'potion' which would improve Auberon's performance and allow him to conceive a child with Cirilla. He also told her the truth (probably to gain her trust) - that Avallac'h would never let her go. Knowing this, Ciri found help with the unicorns where she also met Horsey/Ihuarraquax, by then fully grown. The unicorns explained that both Fox and Sparrowhawk had once possessed The Gate of the Worlds, a mystical power known only to those of the Elder Blood but they had lost it. Now they wanted these powers back and for that they needed Ciri. This could not be allowed, however and the unicorns explained to Cirilla how she should escape.
That same day Ciri once again visited Auberon only to find that he had drunk the 'potion' given to him by Eredin. Unknown to Sparrowhawk it happened to be too strong and killed Auberon. That night Ciri attempted to escape Tir na Lia and its barrier by using a boat and swimming with the river's current. She was stopped by Eredin who then revealed his true intentions, being the same as Avallac'h's. The two battled and Ciri proved victorious due to the elf's underestimation of her abilities - she wounded him and threw him into the river. Later on she mounted Kelpie and rode away from Tir na Lia. She met Horsey who offered his help (actually his being by Ciri's side was a part of her bargain with the other unicorns). They came across a huge pile of bones. To her horror, Ciri realised that the skulls had human teeth making them a pile of human bones. Ihuarraquax explained that it had been a human world until the elves led by Fox and Sparrowhawk arrived and killed them all - this also would be the fate of other worlds, including Ciri's own, should Avallac'h and Eredin succeed in once again harnessing the power of time and space. Nevertheless, Ihuarraquax and Ciri realised that they were being chased. Horsey urged Ciri to jump to another world - the only way to escape. She, however didn't know how. The unicorn became her guide and they jumped. This led to the manifestation of Ciri's strongest power, giving her the title of The Lady of the Worlds. That power allowed her to traverse space and time at will. Not being able to control it, however, Ciri had to journey through many different worlds to finally find her own.
At the Stygga castle, Bonhart died at the hand of Ciri.
"Ahem... Long ago, in a valley far away, lived a girl. She was a true princess, sorceress and witcheress..."
Geralt: "All three? Isn't that a bit much?"
Innkeeper: "Don't interrupt. You want to hear the story or not?"
Geralt: "I won't interrupt again."
Innkeeper: "A story about destiny might prove useful, witcher.
She was born a princess who wanted for nothing, had loving parents and a grandmother who was a great queen. She lived in palaces guarded by hundreds of knights. Everyone thought she'd become a powerful queen. But fate had other plans. Her parents died. Enemies butchered her grandmother and took the kingdom. Still, the princess survived. Her fate became bound to one particular witcher. She gained a new family at Kaer Morhen, the hold of the witchers. She learned to fight. Yet destiny once again made noise.
The lass had magical talent. She was a source. The witchers afeared the uncontrolled power of a source and needed a sorceress to assist them. She studied arcane magic. The sorceress loved a witcher and the two adopted the girl. She was truly happy and could have become a powerful sorceress...
But war broke out and fate separated the family. Aggrieved, the lass disawoved magic and became a huntress, learning to love killing. Death followed her - everyone she'd loved had died. Only the witcher and the sorceress denied Death's calling. Fate cast her to foreign shores, yet she returned. The worst assassin tailed her, yet she emerged victorious. Agents of all kingdoms pursued her, yet none caught her.
When she killed all her enemies and peace descended upon the world, she rejoined the witcher and sorceress, only to have destiny sneer at her again."
Geralt: "What happened?"
Innkeeper: "A peasant unskilled in arms killed the witcher. The sorceress died trying to revive him. The girl could do nothing for she'd disawoved magic. So the princess who would not rule, the witcheress who fought humans, and the sorceress who cast no spells used her power as a means to leave this world."
Geralt: "I sense you haven't told all."
Innkeeper: "All but one. Her name was Cirilla. What's that matter?"