Bloodied Dagger is one of Xanthe's Excavations events. You clear a dig site and face Armaya, Scholar of the Occult, but the real prize stays sealed unless you question the right soul.
Fight through the excavation and defeat Armaya. Pick up the note in the final chamber. Then equip the Ritual Dagger as a catalyst and cast Compel Soul on her assistant's body.
Compel Soul is a human hex, so come back by day if you finish the fight at night. Skipping the questioning leaves the loot locked away.
Image: Rebel Wolves / Bandai NamcoAmbrus's Cellars
Ambrus's Cellars are the court activities where you raid the hidden blood stores of the vampire Ambrus. Each cellar you clear raises his anger, which is how you unlock the duel with him.
Image: Rebel Wolves / Bandai NamcoAmbrus's Cellars: Trouble Brewing
Trouble Brewing is the Ambrus cellar hidden in a guarded house in Svartrau City. Spare the alchemist upstairs and you walk away with a Lasting Malediction Manual and a potent Razor Claw vial.
Ambrus's Cellars: Uninvited
Uninvited is the Ambrus cellar near St. Tyna's Grove, an outpost with ruins below it. It is the toughest of the three cellars because a named murohn guards the blood stock.
Image: Rebel Wolves / Bandai NamcoAmbrus's Dungeons
Ambrus's Dungeons are court activities where you break into Ambrus's prisons and decide what happens to the people inside. They count toward his anger, which unlocks the duel with him.