Very few MMOs have tried to tackle the thorny problem of interaction between players and NPCs except to give the player the ability to kill the NPC, which has not advanced in its own communicative abilities for the last decade or so. We're changing that.
Dialog trees are a new fad providing scripted dialog, but Epic Frontiers takes this technology to a new level with Interrogative, the technology behind the NPC conversation system...
In Epic Frontiers, players are able to approach an NPC and begin a conversation about just about any topic concerning the gameworld. Using the simple interface, the player is able to direct "Dialog Actions" at a subject of conversation (called a "Context"), and elicit a response from an NPC. NPCs can do the same in search of information from a player. Using these simple actions, a player can engage in deep, meaningful, and fast conversation with NPCs regarding various subjects, or even objects in the gameworld, which can be referenced as a Context.

Where missions are concerned, the player can leverage a combination of Dialog Actions and "soft skills" such as Intimidate to gain more information from reluctant NPCs, or convince NPCs of their cover in order to gain their trust. AI based on personality traits allow for missions involving intrigue, espionage, and wits, in addition to the usual combat-based goals. These systems allow for you to build complex relationships with the NPCs of the gameworld, and the NPCs have the ability to remember you in a way that reflects their experiences with you beyond the normal reputation systems currently offered.