Kaderin the Cold Hearted was known as the Kind Hearted until a millenia ago she spared a Vampire in battle and he killed her triplet sisters, Dasha and Rika. Her grief was great enough to debilitate her and her Valkyrie sisters, but she was too strong too die of the sorrow.
A mysterious benefactor, later revealed to be Riora, Goddess of Impossibility removed her emotions, Kaderin considered this a blessing. It was also implied that the blessing was not supposed to remove all her emotions.
Left with cold logic, Kaderin tortured the Vampire who killed her sisters until he begged for death and then allowed him to go into the sun. She also won the Talisman's Hie five times. Without emotions, Kaderin didn't under go any aversion training for diamonds or jewellery.
Sebastian found her at the Talisman's Hie opening ceremony and enter to aid her. She was killed by the Fyre Serpénte after Nix saw her death (the first time Nix has ever done so). She was saved by Sebastian who went on to win that Talisman's Hie and use the prize, Thrane's Key to go back in time and prevent her death.
She is Mated to Sebastian Wroth.