Quote Originally Posted by Vork
In MTW the effects of most vices and virtues are easily figured out because they are listed as e.g. "-1 Valour" or "+2 Piety", but there are a few, such as "Secret Blackmailer" which don't have such effects in their description.

How do I find out what such Vices or Virtues do?

Vork
As far as I can tell, the only effect of the "Secret" vices is that you can count on the vice become exposed at some point. So, you can count on a general with the "secret blackmailer" vice developing the regular "blackmailer" vice (with the corresponding reduction in loyalty to your king) later on. Possibly next turn, possibly many years later.

I never found much benefit to taking the time to expose a general's secret vice. An interesting feature of the game, but I thought it was micro-managing for very little result, if any.