There are two more compendiums. I'm guessing one of the compendiums refers to angels, and Amanda Tapping's character (whether her position is an old one or a new one in heaven) has access to some of the knowledge in that compendium (particularly in regards to how to manipulate angels). We don't really know if her powers extend to direct confrontation with non-angels.
Side note: I'm going to go out on a limb and say the fourth compendium is about humans.
That pretty much covers the major creations. Though, I suppose God and/or gods (plural) is another possibility, and a compendium about monsters in general would be useful.