[Jiggymike]

Looks like Cthulhu made his flush, that's the only thing I could imagine him cold-calling with on the flop, although he might have a set and have tried to raise the turn to get rid of the Ah. Still I think you played this fine, you could have even reraised flop but without nut flush I think this is all good. Cthulhu might have worse flush than you, just keep betting, sometimes a higher flush beats you, usually it doesn't.