The Butchering Knife is a powerful tool that will keep you alive in the toughest of battles. This massive blade counts as a greataxe and has the added ability of giving you 1% of your health back each time you hit an enemy. This weapon comes with the sacred enchantment on it and the Barbaric Roar weapon art that increases your attack power. You can change the enchantment and weapon art and it is recommended to choose one that hits multiple times to get as much health back as possible. Here is how you can get the Butchering Knife in Elden Ring.
To obtain this weapon, you will need to make your way to Altus Plateau. This is the area to the north of both Limgrave and Liurnia. You can reach this area by obtaining both halves of the Dectus Medallion from Fort Haight and Fort Faroth. Once you have both halves, you can use the medallion to activate the Grand Lift of Dectus in norther Liurnia to reach the plateau. You can also take the route through the dungeon that connect the Liurnia ravine to the plateau. This route is not recommended if you are new to the game or are under-leveled.
Once you reach the plateau, you will want to take the long path around the forest in the center like you are going to Mt. Gelmir. After crossing the Bridge of Iniquity, you will come across an area with a bunch of Abductor Virgins. In this area, you will find an NPC invader named Anastasia Tarnished-Eater. You might remember her if she invaded you at the Smoldering Church. Defeat this NPC invader and you will receive the Sacred Butchering Knife. You can take it back to the blacksmith in Roundtable Hold to change the weapon art and enchantment as you see fit.