Medb has her entire life had a fascination with death, skeletons, destruction and most other dark things.
It is because of this love of death that the Lord Weird took interest in her and made her a priestess. After training for most of her life, Medb was chosen to become the bride of the Crom and sacrificed in a giant wickerman.
She was set free by Slaine and harbours a great hate for him for killing her dreams and stopping her from becoming a goddess.