Dragon Age II: Mark of the Assassin is a DLC (downloadable content) for Dragon Age II. After being set up by Antivan Crows, Hawke meets the Elven woman Tallis who hires him to rob an Orlesian noble, Duke Prosper. The goal is a jewel named Heart of the Many and the reason why she chose Hawke is because he received an invitation to participate in a Wyvern hunt. Tallis, a rogue, is force-joined the party during the course of the story and leaves at the end of it.
The DLC takes place in and around the former fortress Chateau Haine, Prosper's current place of residence, and in contrast to the main game (and the DLC content of the predecessor Dragon Age: Origins) all areas are new constructions. The gameplay itself is mixed: it starts with two relatively open areas (comparable to a wilderness area of the main game), a dialogue heavy sequence without fights, puzzles, linear fighting areas and a boss fight to end the expansion. There are also side quests (some can be only played when a certain companions is in the party), optional areas (most of the puzzles take place in those), and sometimes the player can choose how to proceed. Most notably is the choice towards the middle part of the DLC in which the player either can fight through an area or use stealth. Using the latter introduces new gameplay elements: patrolling guards have a line of sight which should not be entered and they can be distracted or knocked put from behind. Both states only last for a short time before they return to their post. Getting caught simply resets the current area to try again.