Caitha is the Goddess of Tears. She is mentioned in the item descriptions for the Red Tearstone Ring, Blue Tearstone Ring and Caitha's Chime.
She sheds pure tears of blue mourning those who have lost loved ones, and tears as red as blood mourning the undeserving dead. Some say that she is a compassionate being who is with us in times of tragedy, others that she is a demoness guiding us towards those tragedies. Lore about her seems to make a point of presenting conflicting opinions.
Her symbol on the Name-engraved Ring is a curse skull and her chime is only capable of Hexes, not miracles.