Matthias is a villain from Lady Death in the comics. He is a descendant of the fallen angels while in the movie he and Lucifer are the same character.
Classic Lady Death
Matthias was forcibly conscripting peasants into military service as feudal levies. The exact nature of the war that Matthias was prosecuting is unspecified, although evidence from the recent revision of the character by Avatar Press suggests that it may have been one of the Northern Crusades (also known as the Baltic Crusades).
Unknown to his innocent daughter, Matthias had a dark secret. Although congratulated by the Church for his work against the pagans, he was despised by the common folk as a cruel and oppressive tyrant. Matthias was outwardly pious and committed, but secretly dabbled in black magic and demonology. He was actually a descendant of the fallen angels who had led the rebellion against God. By contrast, Hope 's mother was a woman so pure and innocent that her bloodline reached Heaven. Hope's mother died when Hope was still in her late teens, and she was left to live with her father. Matthias's plans were, at one point, found out by one of his knights , who he almost immediately killed.
Eventually, Matthias' cruelty triggered a peasant uprising. Matthias narrowly escaped death at the hands of the rebels by summoning a demon, but Hope was captured by the rebels and accused of witchcraft. Faced with the prospect of execution by burning at the stake, Hope uttered an incantation that she had overheard her father use. This incantation summoned a demon who offered her a bargain – he would rescue her from death if she would renounce her humanity and serve the powers of Hell. Hope accepted the bargain and was transported into the infernal realms.
Now in hell; Matthias took control of the army he bought himself with stolen souls. His daughter who had renounced her humanity as well, was brought before him, but he cast her out of the window. He then marched against Lucifer and seemingly won, but really he lost, Lucifer took his face and played a game with his subjects. Hope, now named Lady Death revealed his charade and destroyed his father as he was released from Lucifer. Matthias however did not die, he lived on in the ground of Endless Graveyard. One time Lady Death was turned into Lady Demon, Matthias took the opportunity to use illusions to trick Lady Demon on releasing him, but failed. He also fought Cremator when Lady Death was absent from hell, but again he failed to get his revenge. When Lady Death was turned back to Hope by Leviatha, Matthias took the opportunity to convince his daughter to renounce her soul as well her humanity. He was interrupted by Michael who banished his elemental form. Next move from Matthias was to convince Cremator to abandon Lady Death, but he again failed. When Lady Death learns that Matthias has a place in her Endless Graveyards, she sought up the mausoleum. Lady Death then hurls Matthias and her sword Nightmare into the void left from hell, when it disappeared.
But Matthias lived yet again, he awoke in Transdaemoniium, he picked up the sword Nightmare and lived there as he could. His peace was interrupted by the last survivors of Asgard; Vandala, her friends, and Purgatori who followed them. Matthias tried to strike down Purgatori, but she had unimaginable power, and turned him back to human. Purgatori then took Nightmare and left him live in Transdaemoniium.
Lady Death: The Movie
In ADV Films Lady Death movie, his role is is similar to how he's depicted in the first part of the comic titled The Reckoning. However the one thing that separates him from his comic counterpart is that he is actually Lucifer.