There's a sweet spot in Dungeons & Dragons around when a character hits level 7 that usually ends around 14. This is when characters start acquiring really cool powers, begin facing down more exotic monsters and get involved in adventures with a broader scope. At 14th level through 20th and beyond, though, character power levels start getting pretty extreme. Such characters are less adventurers than nascent gods whose every move can shake the campaign world to its core; when players can slaughter ancient dragons and credibly challenge the hordes of the Abyss, creating believable and challenging adventures is rather difficult. It's to Obsidian Entertainment's eternal credit that Mask of the Betrayer, the insanely ambitious expansion pack for Neverwinter Nights 2 that's built around such high-level content, is as enjoyable as it is. Unfortunately, some balance, design and technical issues keep it from walking with the Celestials.