According to the press release: The new DLC pack includes one new campaign mission (adding approximately 1.5 hours of additional gameplay), 10 new sandbox-mode maps and 19 new prestige gimmicks for just $3.99 USD. The new content is available for purchase now via the Kalypso Launcher within Dungeons, and will also be available on April 4 via digital distribution services.
You can read Strategy Informer's review of Dungeons here.