The Giant Nougat Monster
The Giant Nougat Monster is found in The Castle. It has 2000HP, and hits for 550HP with enchanted black armor.
It gives you 100,000 candies first kill, then it gets lower each kill, but randomly or depending on time raises the candyprize again.
What you have to do is use the boots to fly above the monster, and let your staff and octopus do the rest. make sure to not touch the very ceiling, or else the octopi will not advance, and will just stand there.
Another technique involves the black demon spell, the enchanted monkey wizard staff, and the rocket boots. Constantly jump with the rocket boots on until you reach the ceiling. Keep jumping and use black demons to kill the monster, while the staff's magic also deals damage.
If you don't have rocket boots, equip boots of introspection and nothing else. Use black demons, set up an obsidian wall, and spam black demons while frequently repairing the obsidian wall. The Giant Nougat Monster should die in about 6 black demons.