Kiyan's curriculum vitae can not be reproduced without significant gaps in the story since the witcher didn't use a journal or diary, but there are certain notes scattered around Velen and Novigrad that help to shape a picture of Kiyan's last days as a witcher.
According to these notes, the chronology began with Kiyan taking on a contract issued by Prince Adrien of the Sea Cats which consisted of killing the participants (one of them was the professor Sigismund Gloger) of an expedition to find a treasure in Est Tayiar. Kiyan fulfilled the contract and then departed aboard the ship Flying Stag, despite being offered a secure post as Adrien's bodyguard.
On this ship, Ireneus var Steingrad had bribed the captain to share a cabin with Kiyan so that he could kidnap the witcher. The mage took notes on Kiyan's actions and then conjured up a storm to open a portal to undisturbedly carry the witcher off to his laboratory below Novigrad. Eventually, Steingard succeeded, even though the storm was stronger than expected and wrecked the Flying Stag, killing the crew.
Kiyan was then misused by Steingard and had been the subject of cruel experiments to test the physical and mental endurance of witchers. He was also interrogated and forced to reveal secrets about witcher training, and the Cat School of Witchers in particular. Steingard was pleased that Kiyan confirmed his theories: that the Cat School has elven origins. Kiyan's body survived the excruciating treatment, however, his mind was overwhelmed by the procedure after four days.
Ireneus var Steingrad continued his study regardless of this fact, turning the former witcher Kiyan into a crazed and tormented shell of his former self, driven only by immense pain. This version of Kiyan, Mad Kiyan, can be found in the abandoned laboratory below Novigrad's Temple Isle, where Geralt of Rivia encounters it. Here, the former witcher can be defeated and killed, relieving Kiyan from his fate.
Mad Kiyan: The demise of a witcher Edit
Mad Kiyan is the crazed and possibly possessed version of the witcher Kiyan of the Cat School. The mage Ireneus var Steingard captured and performed experiments on Kiyan in his laboratory below Novigrad, tormenting both his mind and body beyond recognition. Mad Kiyan is thus an insane shell of the witcher only driven by immense pain and the urge to kill intruders.
Geralt of Rivia can encounter and relieve him from his suffering in the abandoned laboratory below Novigrad. However, Mad Kiyan can prove a serious threat to Geralt since even though the mind of a human being is no longer inhabiting Mad Kiyan´s body, his skills in battle remain. Mad Kiyan can use Signs consisting of a bubble of Quen, a version of Igni and Aard. His blows with a Moonblade are fast and can cause bleeding.
Despite all these skills in battle, Mad Kiyan´s vocabulary is restricted to muttering "No good. No evil. Only pain.", "seems you are bleeding", and "This is not the end." due to the absence of a regular human mind through the excruciating treatment by Ireneus var Steingard.
Professor Sigismund Gloger's notes Edit
The leader of an expedition with the aim to discover a long lost treasure in Est Tayiar was Sigismund Gloger. On this expedition, Kiyan officially had the task to protect the participants but as it turned out, he was operating for another client from the start. His mission consisted of killing the participants and securing the treasure. Sigismund Gloger managed to escape Kiyan, but was then trapped in a sealed room, causing him to starve to death.
Prince Adrien's journal Edit
This journal reveals that Kiyan was intended to kill the expeditioners from the start, as ordered by Adrien. It also gives insight on Kiyan's behavior and character.
Ireneus var Steingard's Notes Edit
These notes detail Steingard's carefully planned abduction of Kiyan aboard the Flying Stag after bribing the captain to put them in the same cabin. He puts a spell on Kiyan and then goes through his belongings, including elven weapon diagrams, which Steingard states confirms his suspicion that the Cat School uses elven weaponry. Steingard then summons a storm and teleports himself and Kiyan to his laboratory.
Ireneus var Steingard's laboratory notebook Edit
In this document, Kiyan´s interrogation, torture, and transformation to Mad Kiyan by the hands of Ireneus var Steingard is described in a precise manner.