Grief
The shell – Winifred Burkle – "lost" her grandfather when she was twelve. He was not really lost, Illyria discovers after several hours of confusion and sorting through sense memory, but rather suffered a coronary event and was buried in an exact location where the shell visited him several times afterwards. How that equated "lost," Illyria does not know, but this was Fred's first encounter with grief.
Grief surrounds her now. It is everywhere, thick and heavy like the air surrounding the sea, and smelling just the same: salty and moody and heavy with the stink of the dead. She is tiring of suffering it, but it emanates constantly from not only most of the mortals she is in contact with, but also the half-breeds, which she finds absurd: the shell was food to them; it is ridiculous for them to "mourn" it.
She cannot fathom the function of grief. What purpose is there to mourning something? It does not provide strength, like anger, nor does it provide any sort of reproductive function, like lust.
There is no purpose to grief, and yet it keeps coming and coming.
She is tiring of suffering it.