I think we should start with a relatively simpler system where every region has one primary and two secondary patron deities assigned to it. When I say 'region', I mean the ones distance-related systems like gweths rely on. Because it's not realistic to find a region for each of the 39 immortals in a way that makes sense, all aspects of any given patron deity would also be considered patrons in that region for mechanical purposes.
After such a system is in place, there could be abilities and rituals for Clerics and Paladins which utilize it.
In the distant future, altar creation and player worshipping could affect the influences. This way, when Asketi strikes a major city for irreverence every year, it would be based on truth instead of arbitrariness.
As to what kind of actual effects/blessings a deity's influence would bring... That would be something extremely difficult to determine and balance, but not terribly necessary.
As part of the initial system, a Cleric would be granted the Perceive Divine ability at 20th circle, which lets them sense (1) the patron deity of the region, (2) two lesser influences, (3) followers of the patron deity present within the region. This ability would use/teach PP and Theosophy, and could give tiered information similar to Recall Immortal.
>perceive divine
You sense that Harawep's influence swathes this region like vast, intricate webs. Your mind's eye reveals you the mortal souls who add more silky strands to the goddess' spectral webwork as symbolic embodiments of Her.
You are able to identify the spiritual spiders as Smegul, Teel and Bob.
You also sense the lesser influences of Everild and Alamhif.
In a room dedicated to a specific deity:
>perceive divine
You sense that this is a sacred place.
The presence of Ushnish is overwhelming here, and you are unable to sense any other influences.
Some examplary regional influences I would imagine:
Patron | Lesser | Lesser | |
Crossing | Truffenyi | Tamsine | Glythtide |
Aesry | Eluned | Peri'el | Faenella |
Vela*'*tohr Region | Asketi | Zachriedek | Kuniyo |
Zaulfung | Urrem'tier | none | none |
~Aeth