Master Assassins are not placed on the battlefield at the start of the game. Instead, they are 'hidden' within a friendly Skaven unit whose troop type is infantry and that has a Unit Strength of ten or more. Make a note of which unit each Master Assassin is hiding within. A hidden Master Assassin may be revealed during any Start of Turn sub-phase or at the start of any Combat phase. Position the revealed Master Assassin as you would a character that has joined the unit.

If a unit in which a Master Assassin is hiding is destroyed or flees the battlefield before the Master Assassin is revealed, the Master Assassin is removed as a casualty. A Master Assassin cannot be your army General.