Simplify the following text for a Grade 8 native English-speaking person.
Original: While the particulars of their relationship with Cthulhu are unknown , it is clear that they arrived on Earth with him , where they constructed the city of R ` lyeh .
Simplified: In one of Lovecraft 's tales , The Call of Cthulhu , he said that Cthulhu currently lies in a dreamlike state in the sunken city of R ` lyeh ( rill-ee-yeh ) , waiting for the time when the Old Ones shall rise again . R ` lyeh is located in the Pacific Ocean ( though it is not a real city ) .