Alma is basically the heart and soul of Book 2. Alma, whose name means "soul," represents the complex and abstract concept of the human soul in Christian belief. Basically, the soul is what gives human beings life and what lives on after you die. The soul is kind of a big deal.
It's fitting for Alma to live in, and run, a castle that mimics the construction of the human body: watch-tower for eyes, kitchen for stomach, etc. And she's at the center of it all since the soul was understood to inhabit each person as an animating force ("anima," the root of "animating" also means soul—cool, right?).
But Alma doesn't run things completely on her own. She also has help from three counselors: Phantastes, an unnamed counselor, and Eumnestes. Phantastes, whose name means "imagination," helps Alma with the creative side of things, and with planning for the future. The middle one helps her keep track of what's going on in the present, and Eumnestes, an old man whose name means "memory," helps her keep track of the past. We think she's pretty much got her bases covered.