Ryuk is one the the main character of death note and is a Shinigami (god of death) and lives in the Shinigami realm ( in the abridged the Shinigami realm is just Wyoming) and drops his death note into the human realm simply because he’s bored. as the Shinigami realm is mostly empty with nothing to do, so he goes along with Light just for the entertainment. since Ryuk looks wacky you don’t need to sound a certain way to voice him, you can try to stay close to how he sounds like in the show or just go crazy and come up with your own voice for the character, either or is fine