The central symbol of the Fellowship of Isis is the Cosmic Web diagram, seen
The 4 coils of Tiamat progress from the physical plane outermost clockwise into the etheric/astral, then the mental, and finally the spiritual innermost. You can travel either direction around the spiral, clockwise or counter-clockwise depending on the kind of experiences you are after, although the progression clockwise does run from easier to harder.
Similarly, the 8 rays of the star of Ishtar cross the 4 levels or coils, and mysteries get more complex as you move inward on each ray. Starting with the white ray at the top (North) and going clockwise, you get the Red ray at Northeast, the Orange ray at East, the Yellow ray at Southeast, the Green ray at South, the Blue ray at Southwest, the Indigo ray at West, and the Violet ray at Northwest. These also correspond to times of the year according to the 8-point solar calendar with Yule at the top around to Sahmain at violet in the northwest. There are also associations with the Sun, Moon, and planets attached to each of the rays, as will become apparent as we study the rituals associated with the diagram.
Let's look at the first set of rituals from Dea, which comprise those on the outermost or physical spiral of Tiamat. Ritual #1 is the Rite of Rebirth, which is the ritual intended for initiating a person into studying for the FOI priesthood. It turns the individual inward for spiritual growth along the lines of listening for which goddesses want the initiate to serve them and how. It is located at point 1 on outer edge of the Green ray at South.
Ritual #2 is the Ordination of Priestesses and Priests, which confirms the initiate's work is done and they are now a servant of the goddess. It lies on the Blue ray at point #2 Southwest. Ritual #3 is the Isis Wedding Rite, which is the third transitional rite I mentioned last time, and which lies on the Indigo ray at West.
Ritual #4 is the first one that comes from Dea, "The Awakening of Osiris." It lies on the violet ray at Sahmain. Ritual #5 then occupies the white ray at Yule, and is "The Mystery of the Spheres." Ritual #6 is on the Red Ray at Imbolc and is "Mystery of Demeter and Persephone."Ritual #7 is on the Orange Ray at Oestre (Spring Equinox), and is "The Mystery of Eros and Psyche."Ritual #8 is on the Yellow Ray at Beltane, and is the "The Mystery of the Labyrinth."
Notice that all of these outer, physical mysteries are related to major mythic stories that are easy to grasp. That's what the physical plane aspect gives you. Each of the Rays has a certain character according to its color, for example, the Orange Ray has to do with love relationships at different levels. This is the first round, and I will continue with the next, astral/emotional rituals next time.