Hmm. You use the term 'death magic' ... . Is your new term how the others describe them, or how they describe themselves? If it's how others describe them, is the term in use from the beginning, or is it revealed as time goes on? Do the priests of Behira know the real term? That last question also applies if it's how they describe themselves.
Discovering the name could be a major plot point.
Since I don't know where the story is going, I have to offer avenues. These mages use other people, body and soul, as objects of their casting and as tools. They rejoice in destruction, but it seems that there is a guiding drive behind them--which I assume will be a big plot point. They do not obey the common laws that apply to mages, whether malum in se or malum prohibitum. They obey their own drives and imperatives, some of them more freely than others.
Anver has had a quiet semi-apotheosis. Kha has become a lynchpin in a battle that could destroy the gods.
And Geron ... when it was finally time for Geron to act, the crypt was already closed to the way up from the Three Hells. All Geron did was to close the earthy gate--and the crypt remains in the hands of the Three Hells. (I'm also assuming that it's important that there are three.) What happens when the next Master--maybe even Geron himself--dies?