Darian is one of the Avariel, the wary and isolationist winged elves that produced Aerie. He is one of the Talons, an elite order of Avariel warriors that are in many ways the Avariel equivalent of paladins, though the Talons also have much in common with human rangers. He was sent to Myrrhavin to investigate rumors of an Avariel imprisoned within the city, and if appropriate and necessary, effect a rescue. If Charname approaches him, he will request his/her assistance, and afterwards will offer to repay his debt of honor by helping Charname rescue Imoen.
Aside from his extreme distrust of non-Avariel, Darian is bound first and foremost by duty-he is a sworn defender of Myrrhavin, and will go to any lengths to secure Myrrhavin's security and secrecy from other races, which can at times lead to Lawful Neutral behavior-he can and has done questionable things in the name of duty, and tends to take a cold-hearted view of other races. He will openly admit that he is prepared to take deadly action against Charname and the rest of the party if he judges it absolutely necessary for the security of his home. Despite all of this, Darian is a good man at heart-he does have a clearly defined sense of right and wrong (albeit somewhat twisted, given his distinct tendency towards an "Us or Them" mentality), and will gradually come to trust and respect Charname and [most of] the party over the course of SoA, and in ToB, he will fully accept the party as his friends and comrades. Of course, some people (like, say, Edwin) will never trusted.
Darian will romance female PCs of elven, half-elven, or human descent who are of a good alignment. He will develop a friendship with Aerie and potential romance in ToB, and has many banters with other members of the party.