Blessing Star

The  was a crystal or jewel the First Doctor and Susan obtained on the planet Tacunda. It could fundamentally alter the laws of probability surrounding its owner, giving them extraordinary good luck.

In the Doctor's case, it made it more likely that he would be able to pilot the TARDIS to 20th century Earth. Unfortunately, it also had the effect of burning out the navigational system and stranding the travellers in 1963 London. At some point after Susan enrolled at Coal Hill School, she took the Star to school, hoping it would help her fit in. Unfortunately, it only turned her into more of an oddity by making her unnaturally lucky. She cursed the object and buried it in I.M. Foreman's junkyard. After months of trying to effect repairs, the Doctor was approached one night by Ian Chesterton and Barbara Wright, who pushed their way into the TARDIS. He subsequently dematerialised the TARDIS in a hurry, (DW: "An Unearthly Child") leaving the Blessing Star behind.

Later, after Foreman's liquidation of the site, an unnamed "rag and bones man" discovered the Star, still where Susan had buried it. He retained the device and immediately felt his luck shifting. He got married, won substantial sums gambling, and even found that the items he found whilst scavenging were increasingly valuable. One day, he begins to watch the 1966 World Cup and the jewel begins to respond to his fervent wish for England's victory over Germany. As he's watching, the Doctor, fresh from his victory over WOTAN (DW: The War Machines) finds him. The Time Lord has been tracking down the Star so as to tie up loose ends from his last visit to England. To his dismay, he's found the Star too late. By now, the Star has started to overload, as it begins to take in not just the rag and bones man's wishes, but those of people all over England. The Star allows England to make a very close shot into the German goal, but that's as much as the Star can do. It explodes, overwhelmed by the hopes of an entire nation. England go on to win, but without any further help from the Star.

The Doctor returns to the TARDIS, and a fateful meeting with Ben Jackson and Polly Wright, without having reclaimed the Star. (ST: The Rag and Bone Man's Story)

Behind the scenes
The jewel has considerable commonality with the gambling device from Rivals, an episode of Deep Space Nine that long predated the writing of this short story.