Steps:

1. Meet Dung Eater:

* Location: Roundtable HoldLandmark, backside corridor near the Twin Maiden Husks.

* He gives you the Seedbed Curse if you show him a Seedbed Curse item.

2. Find Dung Eater's Body:

* Location: Subterranean Shunning-GroundsDungeon, sewer gaol.

* Use the Sewer-Gaol Key obtained from Dung Eater in Roundtable Hold to unlock the gaol.

* Defeat the Dung Eater for the Omen Set and Sword of Milos.

3. Free Dung Eater:

* Deliver 5 Seedbed Curses to Dung Eater in his body form.

* He offers his Dung Eater Puppet Ashes and moves to Roundtable Hold.

4. Mohg, Lord of Blood fight:

* Dung Eater can be summoned as a cooperator for this fight if he's free in Roundtable HoldLandmark.

5. Morgott, the Omen King fight:

* Dung Eater can be summoned as a cooperator for this fight if he's free in Roundtable HoldLandmark.

6. Consequences:

* If you complete Dung Eater's questline and become Elden Lord, you unlock the Blessing of Despair Ending.

* This ending curses the Lands Between with the Seedbed Curse.

Notes:

* You can invade other players after obtaining the Mohgwyn's Omen Cloth from Dung Eater's body.

* Killing Dung Eater in his body form prevents completing his questline and obtaining his rewards.