When Kairos was twelve years old, he was told by a creature bound to the crypt beneath the palace that he would die when he turned thirteen. He claims that this was "a great gift", as it freed him to act as he wanted rather than changing himself to fit what other expected of him.
Before Kairos, the previous ruler of the City of Helike was mostly a figurehead, who allowed the nobles and the army to run the city. When the nobility realized that Dorian would be a more active ruler, they offered Kairos the chance to become ruler, expecting him to fall into line like the previous ruler had. This plan was largely successful, leading to Dorian being forced out (and taking to role of Exiled Prince in the process) and Kairos being made ruler.
However, once he had taken power, Kairos began to throw his weight around, and when the nobles objected he fed most of them to his dogs in order to force the rest into line. His thirteenth birthday came and went without his prophesied death. This convinced him that Fate is not ineffable or inescapable, and that he had to power to shape it to his will.
Four years later declared war on Procer, and on the Good members of the Free Cities when they voted to block him from pushing the rest of them into war. After announcing his intention that the Free Cities declare war on Procer, he had the representatives of the Good cities poisoned so that they would die after voting against him.
Kairos is unpredictable, though he seems to plan more carefully than he acts as though he has. On several occasions he expresses disappointment in others, especially the leaders of the other Evil Free Cities, for acting overly pragmatic and not doing things for the fun of it or simply because they can.
He has stated that he considers himself the true champion of the Gods Below, and that the other villains of his time have lost their way. He claims that even if they win victories by their methods, that they are not true victories for Evil because they are not done in the right way.
He also seems to have a peculiar disapproval for swearing. In Helike he has made swearing a stoning offense, and he regularly apologizes for using extremely mild words such as "naughty", despite being in a position of power and acting completely unapologetic of murder and similar actions.
Kairos has dark hair and olive-colored skin. He usually wears a broad grin. One of his hands is usually shaking and one of his eyes is always bloodshot. However After causing deaths, especially in a particularly dramatic and Evil manner, his eye grows redder and his hand stops shaking.
Friendship with Kairos seems to have less to do with loyalty or charm and more to do with how much someone amuses him. He has taken on Anaxares as a sort of pet, keeping him with him at all times and naming him as an advisor to the crown. According to Anaxares, just being called advisor by a foreign ruler qualifies as 33 counts of treason, or over 50 if you include foreign collusion. He seems to be entertained by Anaxares' calm and lack of obvious fear.
In addition to commanding the loyal armies of the City of Helike, Kairos name grants him many mystical abilities. Despite being extremely young he is able to contend with multiple heroes and villains. He summoned specters to occupy the White Knights band of heroes, he manages to float above the ground when needed, and he can even manipulate a soldier's soul.
The names power stems from the adherence to over the top villainous actions. Whereas most villains try extremely hard to not monologue or be drawn into suicidal stories the Tyrant embraces his villainous nature and seeks to out do previous warlords of Helike. His name allows him to not only exert influence over his immediate subordinates but to also control structures and to a varying degree the narrative that creation has written.
His first Aspect, Rule, grants him some manner of power over the weather, which he used to defeat the army of Atalante.
His second Aspect, Wish, allows him to glimpse the individual motivations of individuals. By learning of an individuals motive it allows him to understand and subvert the mechanization of his enemies. In understanding their end goal he has a better understanding of there current actions as well as crucial information on how to manipulate them.