What is or would be an appropriate word to describe people deriving purpose from conflict?

With a slight modification in your sentence, you could write:

The sanguinary (or bloodthirsty) person desires conflict more than peace....

I admit that this is rather a toughie. But let me take a shot at it. A blanket term for a conflict-desiring person? Well, one could come up with a slew of adjectives such as combative, bellicose, pugnacious, and suchlike to describe such a tendency. But I believe that doesn't stay faithful to the demands of the question. Fortunately, this question is well within the remit of psychology, and one could justifiably argue that such a temperament is indeed describable.

The highly-accepted Big Five Personality Traits is a very useful taxonomy for personality traits. It whittles down the diverse personality traits to a nifty set of five— hence the name.

The Big Five traits outlined by the theory are:

1. Extraversion (outgoing/energetic vs. solitary/reserved)

2. Agreeableness (friendly/compassionate vs. critical/rational)

3. Openness to experience (inventive/curious vs. consistent/cautious)

4. Conscientiousness (efficient/organized vs. extravagant/careless)

5. Neuroticism (sensitive/nervous vs. resilient/confident)

Antagonism, the low pole of Agreeableness, references traits related to immorality, combativeness, grandiosity, callousness, and distrustfulness. It is a robust correlate of externalizing behaviors such as antisocial behavior, aggression, and substance use; in fact, in many cases, it is the strongest trait correlate. It represents the core of many important and impactful psychopathological constructs (e.g., psychopathy, antisocial and narcissistic personality disorders). It is also central to models of general and disordered personality, psychopathology, and interpersonal behavior.

I believe antagonism faithfully captures the essence of a conflict-desiring personality.