In the film he is played by Jason Flemming.
Malachi was a former healer who made a bargin with the devil. With his new powers he killed people and corrupted others. At some point he met Marcus Kane, the brother of the titular Soloman Kane. Marcus was acidently critically injured by his brother, but when the healers failed to help him, Kane's father asked Malachi to help, but Malachi turned Marcus into an ghoul bound by his will called the Masked Rider, who becomes his second in command.
Over the years, Malachi and his ghoul army terrorized many kingdoms, killing people, abducting them into slavery, corrupting them and turning them into his army as well. Anyone who resistef him, was met with crucifiified. By chance, Soloman Kane, who returned to his anscestrial home, after begining a vow of pacifsm, was taken in by the Crowthorn's a puritan family, after Solomon was attacked by robbers. Shorty afterwards, the Crowthorns are killed by Malachi's followers, exept for Merideth, who was abducted by the Masked Rider and branded a witch. Despite his soul being at risk (Solomon took the vow of pacifism after a close encounter with the Devils Reaper), Solomn renounces the vow and plans on avenging the Crowthorns and rescue Meridith.
On his way, Solomon battles and kills many of Malachi's followers and rescues many of their slaves, but Merideth was not among them. Solomon meets a deranged priest who explains some of Malachi's history to him and later enocunters the gang of robbers, who Solomon kills two of and interrogates the survivor, who tells Solomon that Merideth is dead. Solomon ends up beliving that his quest for redemption falied.
Solomon was proven wrong when Malachi's followers attack a village to crucify, the leaders of the resistance agaisnt Malachi. Solomon was also to be crucified, but finds Meradith in a cage. Solomon breaks himself free but is nearly killed by the ghouls, but rescued by the resistance.
It is revealed that Malachi lives in a castle on Solomons anscestreal home, so Solomon leads the resistance there to confront him. After a encounter with his father, Solomon finally confronts Malachi in a room where he plans on sacrificing Merideth to open the gates of hell. Malachi has Solomon fight the Masked Rider, who Solomon discovered was really his undead brother. After Solomon kills his brother, Malaci summons a large demon to collect Solomon's soul. Kane manages to shoot Malachi in the head, causing the demon to be sucked back into hell, and sacrifices himself to close the portal to Hell. Merideth believed Solomon dead, but Solomon awakens, having redeemed himself.