From the game in Divine Divinity I got impression that death knighs are some kind of humanoid demons or half-demons in armor, clearly not humans. and some of them have personalities - Ryu-Gor, John, unnamed dragon rider near the dwarf inn, they have "guts" and fears to be punished by their mistress (probably Iona). But later on, in the game Divinity: Original Sin, death knights were introduced as a constructs. a-ka golems, created from tenebrium, source magic and some blood.
So, which is true : are they golems with intelligence or living people?