Fred

Fred is a massive demon who was previously trapped inside of a book. He was discovered sitting on a desk inside the fortress at Mt. Illefarn. In a confrontation at the Ruins of Zehir, he was released by Adrian Avenicci. Fred gave Adrian his soul coin in exchange for his freedom.
Adrian decided to turn Fred over to The Lord's Alliance. Weeks later, Adrian lost control of Fred's soul. This led to his involvement in the death of Kash Koren, Jared Koren's father.
He went on to blow up a small village at the request of the Boys, before turning his attention towards the Orb. After learning the party held half of the Orb, he coerced them into lowering the barrier surrounding Ironmaster. They defied him after defeating King Ironside, preventing him from gaining access to the Orb. He subsequently destroyed the village of Kroushan, and began his conquest of the Sword Coast and surrounding regions.
Known about Fred so far:

• He had been trapped in a book for several hundred years.
• He was placed inside the book as punishment for tying orphans together with rope and having a goat drag them off a cliff.
• He seems to be relatively friendly really love killing.
• He is a twisted version of an Abishai.
• His true name is Infr'gedzik.

Infr'gedzik

"Aww c'mon guys, lemme out! Those orphans had it coming!"