First off, this sounds like Yog-Sothoth, but the short story made no reference to Y-S, and the monster in question was not a god. I'm certain the author was not Lovecraft, but I'm kinda/sorta confident I know the author (Robert Bloch) and he was heavily influenced by Lovecraft. It has that vibe but wasn't set in the Twenties or Thirties.
- About a monster that resembles a floating cloud of iridescent silver bubbles.
- Was discovered in an old sea chest, suspected to contain treasure. Seems like it was trapped until the chest was opened.
- The monster eats memories and identities, and gains the victim's knowledge
- Setting was near the sea. I'm remembering beaches and maybe a sea cave
- Time-wise, the setting of the story felt like anywhere from the mid-50's to the mid-60's
- Main character was male, not a villain but felt unsavory.
- Main character had a girlfriend or love interest whose mind is eaten by the monster
- The ending is ambiguous, like the monster might keep going and eat the minds of all life on earth. I.e. there is no explicit resolution. The main character is either eaten or runs for his life.
- I'm pretty sure the author was Robert Bloch, but my search of his stories is inconclusive. I can't find a synopsis of more than a couple of them, and that has not turned up any clues. (It's not "Opener of the Way")
What is the name of this short story? Thank you!