Kreacher - important in DH?

The character in question is that of Black family House elf, Kreacher. "Order of the Phoenix" director David Yates remarked on what J.K. Rowling's reaction was to the possible omission and the article notes:

“It was Kreacher, actually,” director David Yates confirmed to MTV News on Sunday. “We took Kreacher out, and Jo said, ‘Listen guys, you don’t have to put Kreacher back, but I’m just telling you, if you want to kind of keep a thread going for six and seven, you might want Kreacher to come back.’ She basically told us Kreacher plays a role in Seven, in a sense. She hinted. We thought about it for five seconds, and he came back.” What you won’t see in the Kreacher scenes, however, is him squirreling away any artifacts such as, say, a mysterious locket no one can open (see “Elf’s Absence From Next ‘Harry Potter’ Flick Opens Up Plot Questions“). “Bad David!” Daniel Radcliffe, who plays Harry, teased his director about the locket’s absence. “It was kind of tricky to raise that in our story, because it’s for so much later,” Yates said. “We figured we can probably introduce it later, and that’s the approach we took.”