One day, Loki offered her a potion he'd brewed, one that would restore her youth, and keep her next to him as all the years passed. Kriss refused it. She was happy with one life, a blissful life with him, and their family, and then she could go to whatever afterlife there might be with peace and love in her heart. While he was sorely tempted to press the issue, in the end Loki loved her enough to abide by her wishes.
It was only a matter of time before she would meet her end, and when the time came, she shook the hand of the reaper and went with the smile of a life well lived.
He laid her to rest in the garden, where so much of her work had gone. Planted near her stone he brought back crystal flowers from the future, and charged them with love, kindness, and laughter. Still, he missed her.
Days passed with him sitting at the desk, or standing and staring at her picture. The kids kept up the house and grieved together while Loki mourned alone, but some things are more powerful than even death.
Maybe it's that his heart kept calling for her, or that she couldn't stand to see him weep. Maybe she was sent back, to prevent what Loki might become if left too long on his own with the pain of his loss.
With the help of Kriss, yet again, Loki would remember that he was not alone.