A Skull And A Smile

Irasmus was born a peasant - a normal person with dark hair and dark eyes. 

Due to his experiments into death and his study of Necromancy, his life span has not only been unnaturally extended, but most of the color has been drained from him.  His hair and skin washed out to a bone-like color and his eyes a pale wine-ish color.

He looks to be physically in his 40's

Irasmus's approximate age is 934 (it's a running number and may change depending on how I feel about things)

He has a natural skill with Necromancy, and has practiced it for a huge portion of his life, so he's what you would call an expert.

He see's Necromancy as more of a science than a magic, and therefore separates it from the more obvious magics (wizard and sorcerer stuff)

That being said, even after all his years of living and studying, Irasmus is Average at other magics, at best.  He can't really cast anything offensive, but he knows several good spells for running away.  Even they take a lot out of him.

Because of his lack of healing magic, he's studied herbalism and natural medicine at length just in case.  He's no doctor, but he can treat minor wounds and illnesses. 

Irasmus attempts to be friendly and kind unless someone provokes him to be otherwise.  He tends not to talk about Necromancy, as that ends up being a poor icebreaker. 

Getting him angry is ill advised.  An angry master necromancer is a bad thing to face down despite who they are.

He's generally a gentle person, but he's also a bit jaded.  He's been around long enough and seen enough that most things don't scare him.  He does however, know when to be cautious around a being of power, whether he's afraid or not.

He loves studying how living things work.  If given the choice, he prefers hands on study as well.  That doesn't mean he's going to dissect everything he finds, but if that's an option, he'll go for that.