Aarin Gend appears in the Original Campaign of Neverwinter Nights, making his first appearance in Act 2. He is Lord Nasher's spymaster and a former slave. He is actually a prisoner, serving his sentence as a dutiful employee to Neverwinter. His arrest and punishment was due to his association with Randall the Red, a vicious pirate. Aarin Gend is reputed to be a reluctant murderer; he avenged his mother's death by killing his former master, but he is ashamed of the act.
Whilst working for Lord Nasher, before meeting the Player Character, Gend was ordered to kill the leader of Neverwinter's thieves guild, a woman named Calliara. He was able to infiltrate the guild and became close to Calliara, eventually falling in love with her. Gend is unable to betray Lord Nasher and stay with her, however, and tells her he was sent to kill her. With neither willing to change their stance, a duel results, Aarin claiming a bitter victory.
If the PC is female, a romance is playable with Aarin through Acts 2, 3 and 4. Through a series of player-initiated dialogues, Aarin tells the PC about his childhood, his experiences with Randall and his service under Lord Nasher. After these conversations, Aarin will present the PC with an amulet. In Act 3, as long as the female PC has kept the amulet, the romance is continued through more player-initiated dialogues. These centre around the developing relationship between Aarin and the PC, ending in Aarin confessing his love for the PC. In Act 4, one conversation is available to the PC about the situation in a war ravaged Neverwinter. The male counterpart to this is a romance with Aribeth.
Source: Wikipedia, "List of Neverwinter Nights characters", available under the CC-BY-SA License.