The dagger is as sharp as an obsidian knife. You could easily slip it between someone's ribs, like a hot knife into butter. Underneath how many pillows this journal has been secreted? The dagger is much more than a weapon. It helps prepare the kill.
The assassin cuts their own skin with the tip of the blade, and draws out their own blood to be used as ink. The names of future victims and their realms are written on the pages within, and crossed out with the victim's own blood, once they have been slain.
After a victim's name gas been crossed off the list, no one will remember that they ever existed. They will simply be a mystery victim, found in the wrong place, such as in the bed of a king or queen.
In one of the entries within the journal, both the victim's name and their realm have been crossed out. No reference to this realm can be found in the Library of All Worlds, or in the records and spheremaps of the Chamber Platinum.