Simple unmissable story achievement. Just play through the chapter.
You'll start in the room where you fought Ivor. There is some dialogue.
The amulet will glow white and lead you to a spot on the ground on the left side of the screen. You'll dig a hole and then get attacked by bats. Mash
You'll be in the entrance to a large grinder room. Behind you will be some creepers. Fight them off with your weapon of choice.
The credits will appear as you continue fighting monsters with various QTE's.
There will be a minor choice and then you'll fall into some water.
This unlocks after you get sucked into an underwater tube and get a loading screen.