Bethesda just released a trailer for the upcoming DLC for Dishonored called "Dunwall City Trials". The DLC will include 10 challenge maps that challenges your skill in the game's combat, stealth, and overall creativity. Online leaderboards will also be included as well as more trophies/achievements to collect.
This won't be the only DLC releasing for Dishonored. Two more DLC's are in the works and is planned to be released next year. The second DLC will contain a new story mission that revolves around a group of stealth assassin's called The Whalers. Bethesda and Arkane has yet to reveal details for the third content.
Dishonored's 'Dunwall City Trials' DLC will be available on December 11 on Xbox Live, PSN and PC for 400 MS Points or £3.99 / $4.99.