The latest trailer for BioWare's Shadow Realms builds on what we've seen previously, but still doesn't tell us much. The official website, however, has some light to shed:
Shadow Realms has its genesis in old school Dungeons & Dragons.... It is a game that finally fulfills that fantasy of a never-ending RPG where the players meet up regularly to keep their epic adventures going for as long as they want. All the enemies, traps and challenges are squarely in the hands of another player, who controls them just like a Dungeon Master. The monsters and villains are smart and unpredictable, making every battle a test of strategy and power.
Get more info on the game here, or get a look at the gameplay below: