Mr. Ollivander is the eccentric and almost weird wandmaker of Britain. He sells Harry Potter his wand of holly and phoenix feather, and is also the one that tells Harry that the phoenix that gave the feather to Harry's wand gave one other feather: to the wand that would eventually become Lord Voldemort's wand, Harry's nemesis. He is very odd, in looks and mannerisms, but is a good person serving wizardkind and is well liked in the community.
In the sixth book, he's presumably caught by the Death Eathers. In the film he's caught by the werewolf Fenrir Greyback in the attack on Diagon Alley near the beginning of the movie, although his face is not shown. Therefore, he has an important role in the seventh book, as he's a prisoner of Voldemort and is being held in the dungeon of Malfoy Manor. During his imprisonment he is interrogated and tortured by Voldemort to get information about the connection between his and Harry's wands that prevents him from stopping Harry. Ollivander proceeds to tell Voldemort the history of the Elder Wand and how it could possibly be used to defeat Harry. With this information Voldemort proceeds to search out the Elder Wand . During his imprisonment, Ollivander is taken care of by Wormtail, aka, Peter Pettigrew
Later, he's rescued by Harry, Ron and Hermione, along with help from Dean Thomas, Luna Lovegood, Dobby the House Elf, and Griphook, the goblin from Gringotts. In Shell Cottage, the home of Bill Weasley and Fleur Delacour. During their stay at Shell Cottage, Harry questions Ollivander about Voldemort's intentions and the reason for why Harry's want acts differently in the presence of Voldemorts want. Ollivander is so weak during the final battle that he cannot help with the defense of Hogwarts.. It is presumed that he continued his wand business after the war.
Mr. Ollivander appears in 3 of the 7 novels (Sorcerer's Stone, Goblet, Hallows). He is played by John Hurt. He appears in the first, seventh and eighth film.