The Jp Bonepillar (likely an abbreviation of 'Jumping Bonepillar') is sort of a combination of a Bone Pillar and a Scarecrow. It hops around (like a Scarecrow) and spits out flames (like a Bone Pillar). They are only encountered in certain sections of the Shrine of the Apostates in Castle B.
These enemies can be extremely dangerous, as the fireballs they spit deal heavy Fire damage, being able to kill even a high level character in just a few shots, in addition to their somewhat unpredictable jumping behavior. They are not particularly strong, however, and in most cases they can be dealt with in a single hit.
Jp Bonepillars can be very dangerous if the player is not prepared against them, but otherwise, they should not be a serious threat. Their fireballs are launched slightly above Juste's head, and thus can be avoided as long as the player remains on the ground. If one is approaching, just wait for it and strike with the whip, as a single hit is usually enough to destroy them. Special care should be taken when they are met in rooms that have staircases or platforms, though, as this will allow them to shoot fireballs at different heights, making them more difficult to evade.
Spell Fusions that cover the overall area in front of Juste are helpful for dealing with these enemies. The Axe sub-weapon combined with the Ice Book is great for taking care of those jumping in hard-to-reach places from a safe distance.