There are a huge amount of items and consumables in Elden Ring that you will come across in your time with the game. One of these items, Deathroot can be found in most catacombs and certain skeletal boss fights. Here’s what Deathroot is used for in Elden Ring.
After stumbling across a character named D in Western Limgrave, they will talk about how death has plagued the land, and specifically mention Summonwater Village just down the road. If you choose to rest at a Site of Grace and head back to the roundtable Hold after exhausting all dialogue with D, they will be sitting around the main table in the hold.
After talking to D here, they will mark the meeting place for the Beast Clergymen, who will take the Deathroot from you and consume it. After reaching the point on the map, take the Sending portal to the Beasts domain, where you will actually be able to trade your Deathroot in.
Giving one Deathroot will always net your a reward. Mostly its Bestial Incantations. After giving four Deathroot, the next time you enter here, beware because the creature will become hostile towards you.
That’s everything you need to know about Deathroot and what it does in Elden Ring.