Fungus God from Outer Space

The Monster *IS* the Adventure!

The chosen, with ties to magic and the myriad gods, trembled in their beds as an arc of light flashed across the sky, illuming the heavenly bodies before alighting in the Northern plains of the Duchy of Reme bordering the hobgoblin realms of the Deepfells. A great Fungus God from Outer Space now crouches in silence within its crater as an army of star-spawn rises from the putrefied soil.

What purpose drives the colossal horror from beyond space and time?

The answers may only be known by the bravest and most inquisitive of heroes.

Fungus God from Outer Space:
An adventure for 4-6 characters of at least 6th-9th level (Tier 2 characters in 5e).