During Ogre, Ogre gained a half-soul from Chem and became the first night mare to get one and not give it to the Night Stallion, the ruler over the Gourd and Night. Her half-soul allows her to be a physical creature and forces her to be while in light. Her dream was to see a rainbow, but naturally she could not be in Xanth Proper during the day.
During the events in Night Mare Mare Imbrium temporarily became King of Xanth and ended the chain of ten Kings by defeating the Horseman. In the process, she lost her body in the Void. Afterward, she was awarded a position as a day mare.
We find out in Swell Foop that sometime between Night Mare and Faun & Games, Imbrium mated with the Day Stallion. They produced a colt named Palus Putredinis. The Night Stallion killed Palus, and he became a zombie.
In Faun & Games, Imbrium went on an adventure to help Forrest Faun find a Faun for the tree of his lost friend Branch, who was caught in the void. This ended with her becoming a tree nymph for his friends tree and living happily ever after with him.
- Ogre, Ogre
- Night Mare (book), major character
- Crewel Lye: A Caustic Yarn, mention
- Heaven Cent, mention
- Isle of View, mention
- Question Quest
- Demons Don't Dream
- Harpy Thyme, mention
- Roc and a Hard Place, mention
- Yon Ill Wind, mention
- Faun & Games, major character
- Zombie Lover, major character
- Swell Foop
- Up in a Heaval, mention
- Currant Events
- Two to the Fifth