Thirteen

"I dare not, Headmaster! If I join the table, we shall be thirteen! Nothing could be more unlucky! Never forget that when thirteen dine together, the first to rise will be the first to die!"

- Sybill Trelawney describes the misfortune attributed to the number thirteen

Thirteen is a number that is considered by members of both the magical and non-magical communities to be unlucky and to be the cause of suffering and misfortune.

Wizarding community
On Christmas Day, 1993, Sybill Trelawney, professor of Divination at Hogwarts School of Witchcraft and Wizardry joined several of her pupils fellow teachers for Christmas dinner in the castle's Great Hall. She was fearful upon noticing that twelve people were dining in the hall, that were she to sit down, the first of the thirteen seated to rise would be the first to die. Fellow professor Minerva McGonagall expressed doubts regarding her fears. Thirteen people came to collect Harry Potter from 4 Privet Drive for the last time in 1997. It is possible that this contributed to the bad luck experienced by these wizards and witches on this operation. One of the thirteen, Alastor Moody, died that day. Lord Voldemort spent thirteen years of his life without a body and the Death Eaters had not met in his presence for thirteen years before they did so in the Little Hangleton graveyard on 24 June, 1995. Irma Crabbe was thirteen years old when she and her husband Pollux Black had their first child, Walburga in 1925. Peter Pettigrew murdered twelve people after betraying James and Lily Potter, as well as faking his own death. As a result, Sirius Black was wrongly convicted of the murder of thirteen people and imprisoned in Azkaban. Barty Crouch Jr.'s escape from Azkaban prison in 1982 was not known publicly until 1995, thirteen years later. Lord Voldemort's wand is thirteen and a half inches long.

Thirteen seen in the wizarding world

 * Thirteen people participated in the ill-fated rescue operation in which Harry Potter was collected from 4 Privet Drive and brought to the house of Ted and Andromeda Tonks in 1997.
 * Lord Voldemort was thirteen years without a body after he was ripped from his own by the powerful magic of Lily Evans's sacrifice. This was unfortunate in the extreme for him.
 * Sirius Black's maternal grandmother, Irma Crabbe was only thirteen years old when she gave birth to his mother, Walburga Black.
 * Sirius Black was wrongly convicted of the murder of thirteen people when Peter Pettigrew killed twelve mugles and faked his own death on 1 November 1981. This was extremely unlucky for Black as he spent the next twelve years imprisoned in Azkaban.
 * The escape from Azkaban of Barty Crouch Jr. in 1982 was not publicised until thirteen years afterwards. This in particular was hugely unfortunate for the wizarding world as had Crouch been caught, Lord Voldemort may not have regained his body.