https://deathnote.fandom.com/wiki/Ryuk

Ryuk (リューク, Ryūku) is a Shinigami who indirectly gives Light Yagami a Death Note after becoming bored with the Shinigami Realm. In an effort to amuse himself, he steals a second Death Note and drops it into the Human World for someone to find. This Death Note is discovered by Light, who uses it in an attempt to cleanse the world of evil and injustice, satisfying Ryuk's need for entertainment.