Anemone

Anemone is the only one of her kind around where she resides, she's been alone for as long as she can remember. not many humans come to the beach where she lives and she desperately wants a friend but she always ends up eating or killing everyone she comes across no matter how hard she tries to fight against her urges. there's not a lot for her to do most of the time so she has an underwater cave that she decorates with all the stuff she could find on the people she's had to kill and grieves for them.

Anemone is in a relationship with Gooey, 

they met because Gooey was exposed to Anemone's singing and she helplessly falls in love with Anemone and tries to get close to her, Anemone tries to push her away knowing whats about to come of this due to past experiences, she eventually gives in though as she is incredibly lonely and really enjoys Gooey's company, when the time comes and Anemone goes into a dissociative state and attacks Gooey, she miraculously escapes her death by protecting herself with a force field
long story short Gooey just kills some bloke and tosses him over to Anemone, she eats him and calms down...yes they need to do this on a regular basis....
Gooey basically wants to help Anemone and now actually wants to become better at magic to see if she can find a cure to this curse that Anemone suffers.
This makes Anemone feel incredibly guilty knowing Gooey is probably only with her because of a spell. Does the spell wear off? Who knows. No one has ever lived this long after being exposed to anemone’s song.