The Lord of Blood’s Exultation Talisman is a rather tricky item to find, as it requires navigating through the labyrinth of the Subterranean Shunning-Grounds. You can reach this underground maze from the Avenue Balcony Site of Grace, from which you should go down and towards the left until you come across a well, into which you should plunge. Once in the Subterranean Shunning-Grounds, you will need to make your way to the Leyndell Catacombs, where, after unlocking the giant boss door, you will encounter Esgar, Priest of Blood. Defeating this formidable opponent will drop you the Lord of Blood’s Exultation.