This quest appears in your journal when you get close to one of the locations of Ambrus's dungeons - the places where you complete the following quests: Ambrus's Dungeons: Evil and Convenience, Ambrus's Dungeons: Judge and Executioner, or Ambrus's Dungeons: Twists and Turns.
Ambrus's men have set up a number of heavily guarded outposts - I should find out what they're doing in there.

1. Investigate Ambrus's soldier outposts to learn more
Soldiers in large numbers never bode well... I have to take a closer look.
Kill the soldiers and loot the Directives from Ambrus from one of their bodies.

After reading the note, three new court quests will appear in your journal:

2. Ending
Ambrus's men are draining his prisoners to death, harvesting them for blood, filling entire barrels... This must stop.