Paracelsus is a living demon-axe weapon originally named "Flament Nagel". It originally appeared as a lone violent beast, wandering the no-man's land ruins left in the wake of the Crusades. Slayer, who was wandering around the ruins as well, came across Flament Nagel and the two fought. At first, it appeared the beast was unbeatable, until Slayer discovered it's secret. The body was in fact, a vessel, and inside was a strange, sentient, ancient artifact. After Slayer defeats the relic, he leaves it to it's fate.
Eventually, the flask alcemist, Paracelsus came across the relic on the ground, and brought it back to his laboratory. After Paracelsus created A.B.A, and from their taken away by the military, A.B.A awoke within Frasco, and eventually came across Flament Nagel, and she took him as her weapon and friend, renaming the relic "Paracelsus" in honor of her creator. At least 25 years later, when Paracelsus meets Slayer again, he refers to him as a friend. Bloodstains on the edge of the blade show that he was used as weapon before. A.B.A. later began to refer to Paracelsus as her husband, and has been trying to find a way to convert his body into a human's, and in one of her (possibly non-canon) endings, succeeds in doing this, by bringing Paracelsus to the Post-War Administration Bureau. It appears that Paracelus doesn't want to become a human being, however, and doesn't even really care about A.B.A or her feelings for him either.
Paracelsus has two personalities, one for each of his forms. In his original state, he is silent and doesn't show any signs of evil. He also refuses to have a body of his own, such behavior being most noticeable in one of his quotes (Flesh... I have no need for such a thing.).
In his Moroha form, he names himself "Fighting Spirit", and shows numerous types of violence. He has an unusual desire for blood (which just so happens to be what awakens this form in the first place) and he claims the nearest strongest person as his Master.
Paracelsus cannot fight or move on his own, though he is useful as weapon. His heavy weight causes A.B.A. to move really slow, as it is hard for her to lift him. However, being this heavy, A.B.A's High Slash (HS) deals a good amount of damage. He can be awakened one of two ways. The first one is to feed him a blood pack, which A.B.A. is limited to only three. The other way is to feed him with her enemy's blood. In his awakened form, he becomes really easy to carry and run with. A.B.A.'s combo possibilities and damage output increase as well.
Moroha Form has a further upgrade by using one bloodpack and 50% of the meter, called Goku Moroha. While it decreases some of the damage output, it gives A.B.A. bigger timeframe for Roman Cancels and allows most of her moves to be jump canceled.
Paracelsus seems to be named after Paracelsus, a Renaissance-era scientist/alchemist, who is well-known for his contributions to the field of medicine.
- Paracelsus' voice actor, Toshimichi Mori, also works as the producer and designer of the Blazblue series
- In addition, the character himself makes a cameo in BlazBlue Radio as Mori's chibi avatar when he appears as a guest on the show. This chibi version of Paracelsus sports sunglasses, a reference to how Mori himself is almost never seen without a pair on when in person.
- It has been speculated that Paracelsus may actually be a Jinki, but there is no proof or confirmation of this.
- Despite his stitched mouth, Paracelsus can speak.