William is your butler. Though he always nags you out of love, he is willing to die for you nevertheless. Though only the elites are able to become 'butlers', William is considered to be the cream of the top even amongst the butler association.
William has taken care of you on behalf of your parents since childhood. Loyalty to you, the master, is unquestionable, he tries to protect you by at least risking his life. Although he leads a nannie life more than a butler, he is the elite among the elite who are unrivaled in their abilities as an Unholyc.