Can dementors actually be killed?

[Carol]

No: HPFGUIDX 182394

Jenni from Alabama wrote:

> > I know that a Corporeal Patronus will repel a dementor... but I
don't remember ever reading about one actually killing a dementor. Can
dementors be killed or are they immortal?
 
bboyminn replied:
> 
> Despite the Dementors somewhat vaguely human-ish form, I don't think
they are born (in the normal sense) or that they die. I think it more
likely that they wax and wane with the mood of the times.
> 
> During better times the 100 or so Dementors are content to remain at
Azkaban and feed off their Ministry supplied prey. But as Voldemort
returns and times become darker, and the Dementors are given more free
rein, I think their numbers begin to multiply. Once the dark battles
are ended and people are more pleased and in less of a dark mood,
their number start to fade. 
> 
> Like most creatures their numbers rise and fall with the
availability of food. When the world is in a dark mood they feed of
that darkness multiplying themselves and exaggerating the mood that
supports them. Again, as the dark mood fades, the food supply dries
up, and the Dementor numbers fade.

Carol responds:

I started to reply earlier, but Yahoo!mort ate my post (it has
Dementorish tendencies <eg>), so I'll try again.

I more or less agree with Steve although Dementors flourishing in dark
times again brings up the question of where they find happiness or
excitement to feed on.

Since Dementors are not and have never been human (they're much
taller, have featureless faces with only a gaping hole for a mouth,
create a sense of cold and despair by their mere presence, and don't
require food in a normal sense--neither emotions nor souls have
substance, Horcruxes or no Horcruxes), I don't think that they can be
born or die in a normal sense.

I envision them "breeding" in a figurative sense, manifesting out of a
cloud of fog when people feel despair and returning to nothingness
(unless they have a plentiful supply of happiness to leach out of
their victims and the prospect of an occasional soul to suck, as at
Azkaban), rather like a vanished object in the Ravenclaw riddle in DH.
(I'm sure that there are no male and female Dementors pairing off and
raising families of Dementorlings.)

In both PoA and OoP the Dementors seem to be repelled by Harry's
Patronus, but in PoA, they return to their posts while Harry is
unconscious, and in OoP, the swoop away, defeated. Harry sees the
second one fade into the darkness, but I don't think that it's
disintegrating, only retreating. (Harry is lucky, of course, that
there are only two, but I don't think that Umbridge wanted them to
suck his soul; she only wanted them to force him to cast a corporeal
Patronus so that he could be tried and expelled--and DD discredited.)

I don't think, BTW, that Dementors are "creatures" in the sense of
Beasts; they're not in FB, at any rate. And even though they have
"near-human intelligence," as Umbridge would say (and can somehow
communicate with humans though we never see or hear them doing it), I
can't see even the most fanatical supporter or Beings' Rights
proposing them for representation in the MoM. Maybe they aren't Beings
(like goblins or House-Elves) at all; maybe they're Spirits (the
Department of magical Creatures has Beast, Being, and Spirit divisions).

Carol, heading to the kitchen for a Milky Way (it's too warm for hot
chocolate) after examining Dementors at close range