How to get the Dark Souls 3 Onion Knight Set is as follows:

1. Rescue the Onion Knight in the Jail map and work with the Onion Knight to defeat the Giant Yum.

2. After completing the battle, the Onion Knight sits down in place and talks to him.

3. The Onion Knight thanks the player for his help and gives us Jack's Wine.

4. Light a bonfire and leave the room of the giant Yum, and after some time, the soul of the Onion Knight passes to the player.

5. Return to the Onion Knight's location to pick up props.

6. The Onion Knight will directly drop the Onion Set, and after picking up the props, the Onion Branch is all complete.