I met also that which had been her grandmother. For eighty thousand years Pth’thya-l’yi had lived in Y’ha-nthlei, and thither she had gone back after Obed Marsh was dead. Y’ha-nthlei was not destroyed when the upper-earth men shot death into the sea. It was hurt, but not destroyed. The Deep Ones could never be destroyed, even though the palaeogean magic of the forgotten Old Ones might sometimes check them. For the present they would rest; but some day, if they remembered, they would rise again for the tribute Great Cthulhu craved. It would be a city greater than Innsmouth next time. They had planned to spread, and had brought up that which would help them, but now they must wait once more. For bringing the upper-earth men’s death I must do a penance, but that would not be heavy.

The Shadow over Innsmouth Chapter 5