Dan Sloan was a cargo pilot doing runs from California to South America. During this time, he did some smuggling on the side (antiques, drugs, etc). Some of his dealings were with the Lopez crime family in Rio. He was smuggling drugs into San Francisco for them. He decided to keep some of the wealth for himself and continuously skimmed off the top.
Lopez found out about Sloan's scam and took drastic measures. He had his men shoot down Sloan over the Amazon Jungle. When the plane went up in flames, Lopez' men were sure he was killed. Reality was somewhat different. Dan survived and came out of the jungle with amazing powers albeit a somewhat fractured mind. He couldn't remember anything except his name and that he was a pilot from San Francisco. His body however was incredibly dense and strong. He could leap several miles at a time.
Dan finally made his way to California and was noticed by Raven and Val Cooper. He was initiated into the Dark Force and was given a black jumpsuit of unstable molecules to wear so he wouldn't destroy his clothes. He insisted on putting a strange mask on and called himself Night Breed.
What the team didn't know was that a demon had taken over his body when he was dying. The experience was so traumatic to it that the demon got lost in Dan's consciousness for several months. It wasn't until Dan went into a mystical portal while on a mission in Japan, that the demon awoke and took full control.
Night Breed is now the Night Beast, who serves his dark lord by bringing terror to humanity. He has teamed up with the evil members of Dark Force to achieve this goal.