Why does the Entropy Sphere have fewer options?

[No One of Consequence]

Indeed; the Aided aren't particularly necromantic in their approach to fate. They're very much Euthanatos, in that a significant part of their practices involve determining how one is going to die; but the Aided don't really have much of an association with Agama Sojourns, for instance. Indeed, there are lots of members of the Tradition that I'd never think of as being associated with necromancy; members who are more interested in studying and shaping the effects of fate upon the living, and not just (or even primarily) when death is on the line.

Likewise with the Heirochthonoi: there are, after all, three Fates: one who spins the thread, one who measures it, and one who cuts it. To hear people talk about the Euthanatoi, you'd think that all of the Heirochthonoi worship the thread-cutter. But there's as much in the Tradition about birth and life as there is about death and the afterlife.

Yeah. One of my go to Aided concepts is the traditional old world matchmaker who helps people find their fated romantic partners. Another I like to use for medieval times (or earlier) is the troubador (or bard) helping a knight or other warrior type become a heroic champion. Plus the whole healer side of the Tradition.

(The impression I have of the Aidid is that they see the underworld as this place one sometimes just wanders into, usually while on some sort of quest. Sort of like the faerie lands or the other Otherworlds in Celtic myth.)