So a fan commented that the obscurial in fantastic beasts looked like a baby dementor and JKR said she “liked the thought.” She refused to confirm or deny its correctness/possibility. BUT WHAT IF SHE USES IT OMG.
Dementors don’t yet have a birth story/backstory–and because Hagrid doesn’t keep one as a pet, I assume they live a long time and have a short, dark childhood (because he generally adopts baby creatures.) Beyond that, FB notes that “there used to be more” obscurials, and after a while they stopped occurring so often, likely with the decline/end of popular witch-hunts. Dementors could have a long or eternal natural life, and HP never talks about how to kill them. If FB’s scene of killing the obscurial itself is canon, then it takes immense power to kill one; if an obscurial is a baby dementor, then fully grown dementors would be virtually unkillable. Which would make sense, since HP never talks about how to fully kill a dementor and we can more or less assume it to be impossible.
We know that obscurial children die young. But whether the obscurial itself dies is unclear. Spells can work in the absence/death of a wizard, so why couldn’t obscurials? Remember, they don’t kill Credence in his human form; they strike at the obscurial. They kill the obscurial itself, which may be the only time it can be killed. Obscurial children might not be able to survive if their obscurial is killed, even if the cloud itself is capable of doing so. They’re basically a manifestation of a wizards power, aka a major version of a spell. Because it is a major manifestation, basically a part of the child’s life and soul, I find it totally possible that obscurials become dementors as they age.
TLDR: OBSCURIALS AS BABY DEMENTORS FITS INTO THE HARRY POTTER UNIVERSE LIKE A PERFECT PUZZLE PIECE
This seems quite legit after all we know from the HP world that Dementors are infamous for sucking out all your happy memories and leaving you with nothing but dreadful ones. And we also know from FBAWTFT world that a Obscurial is formed after a child has forcibly restrained themselves from developing their magical powers.
My thoughts are that is it possible that the Dementors are interested in sucking out the happy memories was because when their hosts were alive, they had a rather unpleasant life which in turn causing them to a hole of some sorts that they have the urge to fill up. And hence, the sucking of happy memories from others.


