Death King Blox Fruits: exchange your Bones

Death King is the NPC who transforms your Bones into random rewards. You'll find him in a mausoleum in the Haunted Castle cemetery, in Third Sea. His draw, the Random Surprise, costs 50 Bones and is limited to 10 purchases per 2-hour period, or 500 Bones maximum every 2 hours. During the Halloween event, he also offered a stats refund and a race reroll, but the Fandom specifies that these options have been disabled since the end of the Ghost Event.

How to get it

He awaits you in a mausoleum in the Haunted Castle cemetery, in Third Sea. He lived in First Sea for a long time before being moved in Update 17.

Random Surprise: the 50 Bones draw

Each draw costs 50 Bones and gives you a random item. You can do it 10 times maximum per 2-hour period.

Rarity	What you can get
Common	6,000 to 30,000 Beli
Common	100 to 300 Fragments
Rare	Golden Sunhat
Rare	Bear Ears
Rare	10 minutes of Exp x2
Legendary	Hallow Essence or Fire Essence

The Halloween event version

During the Halloween event, Death King changed appearance. The draw remained at 50 Bones and 10 times per 2 hours, but the table was different and two services were added.

Rarity	What you could get
Common	6,000 to 30,000 Beli
Common	100 to 300 Fragments
Uncommon	10 minutes of Exp 2x
Legendary	Hallow Essence (Third Sea only)
Legendary	A random Blox Fruit, 8% chance

Beyond the draw, he also offered:

Stats Refund: he resets your spent stat points, like Plokster, for 150 Bones.
Race Reroll: he changes your race randomly, like tort, for 300 Bones.

Note: the Fandom contradicts itself on this point - the page describes these three options as available, then states further down that since the end of the Ghost Event players can no longer get a fruit from him and that both the stats refund and race reroll have been disabled. Consider this section as historical until the event is relaunched.

Good to know

The real cap: 50 Bones per purchase, 10 purchases, so 500 Bones maximum every 2 hours.
Fruit draw was removed in Update 17 because Bones were too easy to farm, then temporarily restored in Update 21.
It works on the same principle as Magic Elf.
Display bug: once you've used your 10 purchases, it announces the hours as minutes, like "You currently have 0 purchases left. Come back in 1:59 minutes."
The purple aura he wears on his shoulder is a Roblox catalog item.
The NPC arrived with Update 16.