The symbols on this t-shirt for Potterheads are a number in Ancient Runes : 711. And it is some kind of tribute to Sirius Black, because 711 is both the number of his vault and the page he died (in the original UK version of the book ‘Harry Potter and the Order of the Phoenix’). Wear this t-shirt and don’t let the Muggles get you down !
J.K. Rowling created these Ancient Runes numbers. You could find two pages from ‘Ancient Runes Made Easy’ that explained which symbol stood for which number and why in her previous official website.The numbers are represented by fantastic beasts (here the Unknown and two Unicorns).