The Great One

The adults of Dapto are mentally enslaved by a massive alien being from another dimension to build a structure for its arrival, which turns out to be a dildo for the Great One to pleasure itself with, which would destroy the planet. Ultimately, the Great One is nothing more than a "cosmic fuckboi" that leaves Earth after seeing there are kids, trolling the universe for other planets to have sex with.

Example of:
Lovecraft Lite