Transformation into a vampire

Joachim was not always a vampire and there are many directions to take on how and why he was transformed. What Walter's goal was in turning this young nobleman into a creature of the night, many will never know and only the curious care to dig up reasons for it. Here I'll do just that.

An accident

Many have heard old stories of vampires who stalk beautiful women and create havoc in small, secluded towns. They need only to bite the neck and drink the blood of another to transform the person into one of their kin. There is the possibility that Walter transformed Joachim merely by accident -- only trying to feed off of beauty for the night. However, this spontaneous accident may be faulty in the sense that vampires also create mindless minions from human hosts and therefore lacks a clear way, in this sense, to differentiate between the two during transformation. If you believe in chance, Joachim might have become one of those annoying zombies instead. Woe!

A planned manner

As stated previously, Joachim seems the type that once had control over his own will. Joachim's transformation must have gone beyond a simple bite. Walter could have targeted the young man early on for reasons only he, himself, knew. Perhaps the elder vampire needed a better servant, one he could rely on to do his dirty work. Rituals, though few and far between, exist in vampire lore and Walter may have caught Joachim off-guard and preformed one, making sure that Joachim would keep his sanity even after death, thus making him into a choice partner-in-crime.

A pact with the devil

Or there is a third alternative to this madness. Joachim could have been willing right from the very beginning to be transformed into a vampire, thus aware of the risks he would be taking with his own will and sanity. He might have agreed to enter into a pact with Walter. In exchange for eternal life and power beyond all imagination, Walter would have a powerful ally to participate in his game.

Granted, there are probably many more possibilities and reasons why Joachim became a vampire; some claim intimacy between Joachim and his master and others claim an ill deed done to the young man.