Banor's fate is pretty gloomy and unfortunate.
We can read everywhere that this demigod was loved by his people and has become a great King. His fame made dark gods hate and envy Banor. As the good king was protected by his creators- good gods, he was untouchable by bad goods. This is why the conspiracy and a plan to ruin the good King has been designed.
As a decision- The Dark Woman was created from " thousand mortal slaves as well as the vilest and cunning of their succubus demons". This is possibly how the first Vampire ever was created. Beautiful like none else, seductive and admired by many, she caught the attention of the good King. Banor felt in love her at first sight and immediately decided to marry the Dark Woman. This was the beginning of the Banor's downfall...
Deceived by the beauty, sweet words, compliments and pretentious good nature of the Dark Woman, Banor slowly become fully manipulated by his wife. Once, Good King, Banor become a tyrant to his people- greedy, self-righteous, ignoring the needs of his man and duties as a leader, he was enjoying himself in feasts and splendour. Only once the leaderless armies were severely defeated, Banor realised that he needs to act to protect his country. He decided to join his army in the battle- which was met with protection from the queen. To influence Banor and make him more potent to her manipulations and make him even weaker, she secretly drunk his blood while he was sleeping.
Due to his misdoings and sins, Banor becomes forsaken by gods and steps into the darkness. As The dark woman was sipping his life force every night, Banor grows weaker every single day.
One day the monster which he married made a mistake and drunk more than usual. The shock made Banor see what she truly was. In a rage, he killed his wife with a single blow. Overloaded with the emotion and close losing himself in the madness, Banor decides to drink the blood of the slain wife to become stronger and bring victory in the battle which was just around the corner.
This is how the first human become the first human vampire.
Banor, instead of becoming stronger become weaker... fell into a deep sleep for a long period. Once he has awakened, he was not a human anymore.
It looks that this story is also described in "The Blood curse" book- in slightly different version . Anyhow, both not in Banor's favour.
https://tibia.fandom.com/wiki/The_Dark_Woman_I_(Book)
https://tibia.fandom.com/wiki/The_Dark_Woman_II_(Book)
https://tibia.fandom.com/wiki/The_Dark_Woman_III_(Book)
https://tibia.fandom.com/wiki/The_Blood_Curse_(Book)