So the marshal is like the consigliere of throne of lies.
In this point it has practically a 100% Chance to find out a hidden detail, like prince prison and a persons EXACT class.
What I think:
Night Ability 1
Corrupt Investigation
Learn 2 classes of what target may be
(This replaces probe)
Day Ability 1
Expose
Exposes your targets day ability, who they target and performed it on
2 Uses
(This is a nerfed expose)
Those are my ideas