"The Following ranks are accepted into the Guild (in order of seniority): Rogue, Senior Rogue, Swindler, Seasoned Swindler, Cutthroat, Senior Cutthroat and Cutthroat of the Filled Sack. You can address the guild members from Rogue to Seasoned Swindler by their rank or simply as "Rogue". The Guild members ranked Cutthroat and Senior Cutthroat shall be adressed by their rank, as "Madame Thief" or "Your Rogueness". When addressing a Cutthroat of the Full Sack it is mandatory to say "Your Unscrupulousness" -- and pay a small fee."
Excerpt from the Thieves' Guild Statutes.
In order to build a Cutthroat, one must first build a Rogues Guild and Training Grounds.
Strong Poison: Damage: +100% Death Magic.