Laufey, just as Jason said: it is your mod and it is your vision of Edwin, and it is great that you are developing them. So the following are just notes, not critisizm or anything adverse.Well, this is obviously a point where we are going to disagree. I know you consider Edwin to be 'evil to the backbone', but I don't. I see him as being egotistical, certainly, but still capable of being selfless and caring with those rare few individuals he deems worthy of him. (Counted on one hand, admittedly.) I think anybody who isn't a complete psychopath is capable of love, and I don't think Edwin is that. Consider if you will a ruthless mobster, somebody most people would see as 'evil'. Yet he may still love his wife and children, and want to protect them.
And since alignment is only an artificial construct, I believe Edwin might very well fall for a lady paladin, assuming she wasn't of the type who'd prefer to smite him on the spot for being 'evil aligned', but rather tried to draw out his 'softer, gentler side', as Gracie in the Sea's Bounty put it. Besides, I only have the Intelligence restriction, and consider that enough.
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I am not quite sure how an egotistical person can be selfless (I'd call it a contradiction in terms) and Edwin is the epitomy of egoism. Basically, his attachment to whores/chambermaids coming streight out of there: that type of man prefers woman below them in social status/intellect/beauty/everything, so I actually think that your restriction on intelligence is well...not warrented.
Every parameter of NPC is an "artificial constraint" defining certain characteristic of an NPC - what can we do - it is a game! Alignment defines his/her outlook on life and relationship with society and others. You would not expect a character with 5 strength to use a two-handed sword. You would not expect a person with lore of 0 to identify Equilizer's pommel jewel. So why would you expect a lawful servant of evil to fall for a paladin, and vice versa? My understanding is that a paladin/any good character would attempt to surrender Edwin to authorities based on his attempted murder of Dynaheir, attempt to hire you as a killer and his attempt to kill you when you refuse to be a murderer.
Now, if you say Edwin is not exactly evil character, than well, you are departing from in-game Edwin and using "in the cards edwin". So basically what it all boils down to is may be it is sort of warranted to switch his starting alignment to LN?