Q) From the quest [A Special Surprise] a [worgen][death knight] could learn from [Lord Harford] that they were [servants of Arugal] before their death and resurrection. But, how did they keep their humanity and intelligence without drinking the Ritual Water?
A) When the player death knights are pressed into the service of the Lich King, their minds are flooded with his indomitable will. The mind of a worgen who has not undergone the purification ritual beneath [Tal’doren] is in a state of constant battle between the wild, animal instincts of the [curse] and the rational mind of a human. Almost invariably, the curse overwhelms the human mind and renders the worgen little more than a ravenous beast. With the addition of the Lich King’s control, however, the instincts of the curse are shattered by his power, leaving the logical, human mind in the service of the [Scourge]. And with the Lich King’s will removed, as was the case with the [Knights of the Ebon Blade] at [Light’s Hope Chapel] , only the human portions of the mind remain, giving the now free, undead worgen control over its destiny. Similarly, the Forsaken discovered that the [Archmage Arugal] had access to enchantments that allowed his favored worgen servants- which included Lord Harford- to retain a fair deal of their human intelligence as well. The source of these enchantments remains a mystery to this day, as Arugal took these secrets with him to his grave.
I am gonna leave it here for posterity because I discovered this piece of information by mistake. Kinda interesting information that made me look at DK Worgens differently~ Now only Lightforged will annoy me.