Since killing things at the rate that players do here to XP would "normally" have you locked away as being a homicidal maniac the alignment system works by ranking players based on how evil they are. The 1/3 of players who are the most evil are classed as "evil" The 1/3 of players who are least evil are ranked as "good" The remainder are "neutral". Attacking a good creature is an evil act. Doing this more than 2/3 of the other players do makes you "evil". Attack fewer than 2/3 of other players and you rate "good". Being attacked and defending yourself isn't an innately evil act. Unlike most MUD's just attacking evil creatures has no effect on your alignment. You are all evil SOB's, it's a matter of HOW evil.