The blood talisman is an item that allows players to enter the Blood Altar located beneath Meiyerditch. It can be combined with a tiara to make a blood tiara for 52.5 Runecraftingexperience at the Blood Altar by using the tiara on the altar. Both the tiara and the talisman allow players to train the Runecrafting skill.
Before the official release of Legacy of Seergaze, image of the blood talisman was discovered on the Jagex website before its release via URL manipulation, leading many at the time to believe blood runecrafting would be made available quickly. Jagex later removed the blood talisman image from the website.
The blood talisman was referenced long before its release by the dwarf Thorgel in the Mourning's End Part II quest. You take a list of items to him in exchange for a death talisman, but if you ask why he wants the items, if one of them is a jail key, he will say "Pretty please with a blood talisman on top?" at which point the player exclaims "A Blood Talisman!?" and he replies "Oops! I meant Death Talisman!" with a very shifty look on his face.