Satan

"I am Satan the arch enemy of the Universe"

—Satan, Summoner Saga Endless Chapter 8 Final

History
Satan commonly know as the Devil the prince of Darkness. He is the demon lord who represent the "Wrath" in the seven Deadly sins, the name of Satan mean adversary in Hebrew.

In modern and late Medieval Christian thought, Lucifer is a fallen angel commonly associated with Satan,although in the Medieval Christian for a moment was considered as canonical the name of Satanael as the original name of Satan when he was in the heaven, Satanael before Michael removed the -el suffix (signifying the loss of his angelic nature) and sealed him in Hell..

Equal that Lucifer, Satan or better said Satanael created a rebelation againts GOD in the second book of Enoc,maybe was that the motif why Satan and Lucifer are considered the same evil entity,

Satan could have his origin in the Zoroastrian Mythology with Ahriman,but also with other similars gods for example Hades/Pluto from Greco-Roman Mythology, Seth from Egiptian Mythology and Mara from Buddhist Mythology and even with some Angels as Samael and Mastema

For a moment Lucifer was a poetic appellation of Satan, in the book of apocalypse Satan back to the earth in the final judgment

General
Satan is the Darkness of Lucifer, he is the creator of philosofal stones

Summoner Saga Endless 7 & 8
in Summoner Saga Endless 7 Satan appears at the end of the game as the next villain after that killed to Lucifer, in chapter 8 final he is the final boss