Mechanics
The three gates every class trainer checks
Every unlock runs through the same three checks. [1]
Details
Sins come from killing other players. Offerings come from orderly work, mostly quests and bounty-style tasks like jailing outlaws. Most classes want 30 of one or the other. [2]
Each class attaches its own task, and difficulty varies wildly. [3]
Trainers charge a fee on top of the alignment cost, and 1,000 silver covers the documented ones. [4]
References
Community documentation; not tested in-game. Patch not stated. Sources checked .