There is no alignment system in place yet, however there are some spells/systems that will recognize your last favor- so if you wish a dark aspect, get a favor from your favorite dark god.

Whenever I enter the Crossing Cleric Guild I'm greeted by the following:

The monk makes a sweeping gesture with his hand, ushering you toward the guildhall with the words, "Welcome, (name)! It is good to see you visit us still, even as you grow in the eyes of Urrem'tier."

However, for the past 20 circles I've switched all prayers from Urrem'tier to his dark aspect, Aldauth. Will my alignment in this regard ever change to Aldauth, or is it based solely on worship of a neutral aspect?

>>As I recall, its based upon the last favor orb you sacrificed. Try filling an Aldauth orb and sacrificing it. >>

That is correct. Whatever God of the last favor orb you use is the one you will get that message from. If you choose a dark aspect, some of your spell messaging will change.

Vulture primers and beads... easiest to get and what I use to get my shiny favors of painful death.