There are many Incantations that you can get in Elden ring, and this is one of the most powerful that you can get your hands on. If you are going for a faith-based build, you will want to make the journey down to the Crucible Knight. Here is where you can find the Aspect of the Crucible: Horns Incantation in Elden Ring.
To start things off, you will want to make your way to the Rampart Tower Site of Grace. This is the Site of Grace at the top of Stormveil Castle. The route that we will take you on starts from this Site of Grace. Be sure to rest before attempting to reach the Crucible Knight.
Start the trek off by going out onto the tower wall. You will see a few of the bird enemies with swords. Be careful, these ones will throw explosive barrels at you. Take them out from afar if you can to minimize the damage you receive. Head over to where the third bird waits. It can be found on the left side of the wall in the part that juts out. Hop up on the wall and look down. You should see a platform below. Slowly walk off to land on it.
Follow the ledge over to the castle wall. You will see another ledge you can jump on that leads over to a small tower. Jump onto the ledge and roll off onto the small tower. Jump down to the ground below. Once on the cliffs below, look over the edge from another ledge you can jump down to. When you land on the ledge, it will break and you will start a freefall, landing in a patch of vegetation below.
Walk forward to find the Crucible Knight. He will walk through the archway and stop in front of an item along the cliff face. Wait for him to stop to get a solid strike to his back in. This enemy is hard to take down but use the environment to your advantage and you should be fine. Once the Crucible Knight is defeated, you will receive the incantation.