Elden Ring has all sorts of ingredients to find for your recipe, and one of the most sinister is the Sacramental Bud. You can find it in a hideous place called the Caelid, but we’ll get into the details below.
The Sacramental Bud grows in an ominously named location called the Church of the Plague. It is southeast of the Dragonbarrow West and southwest of the Minor Erdtree in the area. You can also spot it around Mount Gelmir later in the game.
When you get to the area, you’ll see a bunch of white stalks with red berries. In these colors they are dimly lit at night. You are in the church itself and also on the left where the cemetery is. Luckily there are no enemies in this room. However, you may notice a girl warning you to take a step back. She seems to be cursed with something from Caelid territory.
Back to the sacramental bud. It’s an extremely rare item to find, so make sure you don’t waste this valuable resource. You can craft preservative boluses that cure rot. This can be done from the Armorer’s Cookbook  this can be spotted just around the corner to the left of the Siofra River Bank Site of Grace. Beware of two ghosts who will fight against you.
https://www.gamepur.com/guides/where-to-find-sacramental-bud-in-elden-ring-and-what-it-does Where to find Sacramental Bud in Elden Ring – and what it does