Also known as 'Liquid Luck', Felix Felicis was a potion that gave the drinker a spell of luck during which time anything they attempted would be successful. It can be toxic in large quantities and is a banned substance in organised competitions such as Quidditch as a method of cheating. The potion was introduced to Harry and his fellow sixth-years by Professor Slughorn. The new Potions master offered the potion as a prize to the student who brewed the best Draught of Living Death. With a little help from the Half-Blood Prince, Harry secured the prize which he used later in his sixth-year to procure a vital memory from Slughorn as well as to help defend his friends from Death Eaters.