I have two options: When Kreacher allied all the house elfs to battle at the end of the war and he might have not survived. 秒 opinion: Mayeby he survived and went back to the Black House 或者 Grimauld, where he still devoted Ms.Black. Well that's all I can say!
Book wise, he stayed with Harry. Harry actually mentions him after the final battle.
Movie wise... no idea. I assume he's still at Grimauld Place, but they kinda forgot all abot Kreacher when Harry, Ron, and Hermione left for the locket so...
