Adds a few advancements as you can see in the photo above. This includes Killer, which requires to kill a player, and Warden Killer, where you got to kill the warden. Also you have Warden Eater, in which you have to kill the warden by killing it with a trown trident.
You will also have some custom loot tables, which make it worth the effort of killing the warden and aad loot tables to mobs that don't have one.