In the Harry Potter books, the villains of the series are the Death Eaters, a group of Dark Wizards led by the arch-villain, Lord Voldemort. Their name, "Death Eaters" lets you know pretty immediately that something bad is going on. But what exact type of badness is it?
At the beginning of Book 4, when the Death Eaters are first introduced by name, they are engaging in hunting muggles, non-magic users, and from that point on, the main motivating factor amongst the Death Eaters seems to be their hatred of non-wizards, and also wizards who are not pure blood. The wizards are not dark in the traditional sense of consorting with the demonic, or the horrific, but instead have simpler motives: wealth, prestige and the power to inflict cruelty on others. They are just another fascist regime.
And yet, there is that name, "Death Eaters". Although we can't be sure if the rest of the group are motivated by it, we know that Voldemort himself is terrified by the inevitability of death. All of his magical career has been centered around finding more powerful and perverse magics to become immortal. Voldemort is, himself, not even one of the pure bloods his movement values so highly. Does Voldemort believe any of the pure blood talk he proclaims, or is it just a way to manipulate the decadent and rich to fight for him as pawns in his bid for immortality? And, for that matter, are the other wizards around him equally afraid of dying, and similarly concerned with gaining immortality?
I suspect that the two goals are not disparate, but are linked, and that Voldemort does believe his own propaganda. In the final book, when the Death Eaters have gained control, they put up a statue that proclaims "Magic is Might", which would seem to suggest that power is not just a tool, but a goal. The self-image of the Death Eaters is as something powerful, unmoving, unchallenged, and above all, unchanging. By focusing on their group identity as something that can not be threatened, they can all avoid, at least for a while, the inevitability of their deaths.