First this is about LDS Mormonism specifically, groups like Temple Lot that reject the Cosmic Pluralism of Smith and Young's later teachings view Satan about the same as Protestants and Evangelicals who are KJV only do.
Here is a Mormon Website defending Mormonism against this accusation.
Yes it is true that this Mormon doctrine makes all Angels and Humans brothers of Jesus and Lucifer also. And indeed The Bible also calls all Angels including Satan "Sons of God" in Job and Genesis 6. And The New Testament calls Adam and all Believers "Sons of God". And I thank this webpage for reminding me of Hebrews 12:9 and how that could be relevant to the Nephilim view vs Sethite view debate. But also just like in The Bible, Satan has a certain seniority over the others besides Jesus who is the First Born.
My objection to the Mormon view of how Jesus and Satan are related is not so much that it elevates Satan (my view of Satan may well be a more powerful entity then the LDS view, he's the Archon of the Kosmos), it's that it subtly demotes Jesus.
On that very page, in it's answer to "Q. What about the Jesus and Satan being brothers claim?" They say "However, Jesus chose to honor and glorify his Father while Satan chose
to rebel against and dishonor Him. Jesus and Satan are polar
opposites–literally as different as any two individuals can possibly
be." Meaning they're arguing the difference between Jesus and Satan begins with the choices they made, they were equal in Creation. I believe Jesus is the ONLY Begotten Son of God, John 3:16, not just the First Born, though First Born of Creation is also one of his titles. He is The Word made Flesh.
The LDS view of Jesus and Lucifer is not unlike Manwe and Melkor in Tolkien's cosmology. All the Anuir were created from the thoughts of Eru Iluvatar, but Manwe and Melkor were twins essentially as the First Born of his thoughts, but it was the choices they made that made them opposites.
I doubt Tolkien was copying Mormonism specifically, he was drawing on mythological motifs that are common and Ancient. From Thor and Loki as rival sons of Odin to Vishnu and Shiva of Hinudism. And the Zurvanism form of Zoroastrianism has Zurvan in the Elohim role, and Ahura-Mazda and Angra Manyu as the good and evil rivals he created.
But the beginning of this motif is perhaps Enlil and Enki as the chief sons of Anu in Sumerian Mythology. Just do a Google search with Enlil, Enki and either Satan or Lucifer as the main keywords and you'll find many websites and articles saying Enlil is like Yahuah/Yahweh (LDS Mormons believe Jesus is Jehovah while Elohim is God The Father) and Enki is The Serpent of Genesis 3. Sometimes from Christians saying this is Satan's earliest corruption of the Biblical world view. Meaning they're not saying it's okay to worship Enlil, but that Enlil was devised in some ways to reflect how Satan wants people to view Yahuah. Rob Skiba has also talked about this subject.
There is definitely a subtext to the Sumerian myths that present Enlil as bad compared to Enki. Also the earliest Temple of Eridu (the original Babel) was devoted to Enki. Enki is presented as the one who gave Mankind knowledge and civilization. Enlil is presented as sending the Flood while Enki warned the Noah figure. In Akkadian and some other Semitic Mesopotamian texts Enki is called Ea.
I wonder if Tolkien's account of how Luthien puts Morgoth to sleep to take one of his Silmarils could be his puerile re-imagining of the myth of how Inanna obtained Enki's me.
In the Baal Cycle and other texts of Ugarit, the Enlil role seems to be played by Baal (sometimes also called Hadad/Hadar/Adad/Adar) and the Enki role by Yam and maybe also Lotan, scholars disagree on if Lotan is Yam or an instrument of Yam. And the role of Anu is played by El.
Baal worship is probably the most frequently condemned false Worship in the Hebrew Bible. But remember God dislikes being identified with a Pagan god just as much as being rejected altogether, we see that in the Golden Calf incident where they called the Calf Yahuah.
Hosea 2:16 refers to Baal as a name or title Yahuah has been called, but as one he doesn't like. Of course the main context there is how Ish and Baal are both words for Husband (marriage is the major theme of Hosea) but Baal also means Lord while Ish is a word for man as in male gender that is introduced in Genesis 2. So I see this as mainly being about how the marriage of Genesis 3 will be done away with in favor of the marriage of Genesis 2.
The devout Baal worshipers Ahab and Jezebel named at least three of their children YHWH theophoric names. Athaliah, Ahaziah and Jehoram.
Zachariah 12, I have already talked about before possibly using Hadad-Rimmon as a title or idiom of Christ Crucified.
The Tel Dan Stele was made either by Hazael of Aram-Damascus or by Jehu, both were anointed Kings by Elisha on instructions originally given to Elijah by Yahuah. Both should have known full well that Yahuah made them King, but the author of the Stele says Hadad made him King. Jehu did continue the Sins of Jeroboam.
In Hebrew Lotan could come from putting a Lamed as a prefix before Tan,
the basic root word for Dragon, which would mean "To the Dragon". Some
have connected the Ugarit Lotan to the Biblical Leviathan. The name
Lotan does occur in Genesis 36 in the Horite genealogy.
Isaiah 27:1 has a phrase translated "the dragon that is in the sea". But in the Hebrew this is only three words. "Tanyin asher Yam", Yam being the Hebrew word for the Sea. It could be this whole phrase is a name or title of Satan and that we have a Biblical basis for using Yam as a name for Satan. I notice this could parallel Ehyeh asher Ehyeh "I Am that I Am", maybe it could be "The Dragon that is Yam"?
Psalm 74:13 could also be interesting in this context, and also Ezekiel 29:3. Or Ezekiel 32:2 where the word for Dragon is translated "Whale.
Some Canaanite texts call Yam Judge-Nahar (Nahar being interpreted to mean river) Nahar is a name that could easily be related to Nahash, the word for Serpent in Genesis 3 and 49 and other places. Rivers are Serpent like in a sense.
There is some evidence that Chemosh and Moloch were just the Moabite and Ammonite forms of the same deity. Since Chemosh seems to have been depicted as a Fish god I'd say they're more likely a Yam/Enki figure. And that the Philistine Dagon is the same as them also, Dagon comes from the Hebrew word for fish.
In Egyptian mythology the rival brothers are Osiris and Set.
While we're used to thinking of Set as the Satan figure particularly thanks to Aquino's Temple of Set. In the context of the mythical motifs I'm discussing here, it should be noted that Set slew the Egyptian Lotan figure, the coiling Serpent Apep. And that the Hycsos who came from the Levant seemed to favor Set because he was the easiest to identify with Baal being a storm god, albeit of sand storms. Perhaps the Genesis 36 name Shobal is a shortening of Seth-Baal?
Maybe originally Osiris and Apep were the same or linked, but in time the enemy of the heroic Set and the enemy of the villainous Set were separated. Osiris is often depicted as having Green skin, scholars usually explain this as being because he was a Vegetation god. But I know of no direct connection with vegetation besides that modern comparative mythology logic seems to see every "dying and rising god" as either a vegetation god or a solar god, and the solar motif is taken by Ra and Aten.
The fact that Osiris and Horus are so firmly linked to the person of the Pharaoh himself, makes the possibly of Osiris as a Serpent god interesting in light of Ezekiel 29 and 32. And Egypt is also mentioned in Isaiah 27. And also how Rahab (who is unfortunately sometimes transliterated the same as Rachab) is often interpreted as both a Lotan figure and as a name for Egypt or whoever rules it.
Orisis also has overlooked aspects of being a Goat god, from his connection to The Goat of Mendes, to his name being connected to the Hebrew Seir/Sayir. How does that fit with my having just argued he's a Sea Serpent god? Well the constellation Capricorn is depicted as Half Goat and Half Fish, and it's been depicted that way for over 3000 years. The History and Mythology section of it's Wikipedia page says the Babylonians viewed Capricorn as a depiction of Ea aka Enki.
That can be interesting in light of my argument that every use of "Lamb" in Revelation is perhaps really Goat. We'd have the Second Beast having Goat like Horns but speaking with a Dragon's voice.
Horus could then be equated to Marduk, the son of Enki who in the Enuma Elis takes on the position previously held by Enlil in earlier myths.
However Egyptian mythology can be confusing, partly because it changed over time, and much of it was different tradition of the Upper and Lower kingdoms being fused together. As such another Enki/Yam figure could be Sobek, who was depicted as a Crocodile, and also viewed an an embodiment of The Nile (paralleling Yam as Nahar). And came to be linked to the Pharonic power similarly to Horus and Osiris. And another Enlil/Baal figure could be Amon, who in Carthage was identified with Baal as Baal Hamon, (and with Seux by the Greeks as Zeus-Amon). And another Anu figure could be Atum.
And then there is that one Masonic ritual where the secret word is
JaBalOm which is a merging together of the names of Jehovah, Baal and
Amon into a single name.
Geb/Seb/Keb is also sometimes depicted as a Crocodile or Snake. And he is also described as the Father of Snakes, like Nehebkau. He was the father of Osiris and Isis and Set and Nebthet. Geb is also considered a god of the Earth, and Enki means "Lord of The Earth".
Perhaps and Geb and Sobek were originally the same. Of the sons of Enki, Marduk who went on to take aspects of Enlil could be equated to Set. Dumuzid/Tammuz father is never directly stated, but his sister Ngeshtin-ana is called a daughter of Enki and Ninhurshag. Hislop derived mythology makes Tammuz sound like Horus, but he was actually more like Osiris.
In the Sumerian poem Inana and Bilulu, one figure Inana gets revenge on for being involved in the killing of Dumuzi/Dumuzid is Jirjire, the son of Bilulu. Jirjire is turned into a Desert god of bad weather, making him a lot like Set, a god associate with the Desert and Sand Storms and other bad whether, which is why the Greeks sometimes identified him with Typhon. Marduk seems like a god we only know by the name the Semitic Mesopotamian called him, as if he doesn't go all the way back to Summer. Perhaps Jirjire became Marduk?
Set has somewhat of a minor solar deity association via his riding in Ra's Chariot to battle Apep. Marduk too however is while not the main sun god a name that meant "Solar Bull".
Inanna's position the Anunnaki genealogy is often confused. And I think this comes from the attempts to give aspects of Enlil to Marduk. She is both the direct daughter of Anu, fitting Ashteroth/Astarte of the Canaanite panethon. And a daughter of Ningal and Nanna, perhaps explaining the Greek Asteria who has a name related to Astarte and is a daughter of lunar deities. And her being a twin Sister of Utu may relate her to the Eye of Ra or other feminine solar deities. And she's sometimes a daughter of Enki, making her a sibling possibly of Ngeshtin-ana and possibly Dumuzi, making her fit Isis relationship to Osiris. But I think Isis isn't the only Egyptian goddess who's a reflection of Innana, I think so is Iusaaset and possibly Hathor.
Because Greek mythology (which the Romans copied) did a lot of splitting up mythological roles. The Sea-god (Pontus, Oceanos, Poseiden, Triton, Neptune) and the Dragon/Monster to be slain (Typhon, Ophion, Ladon, Hydra, Cetus) figures become firmly separated. So that in Tolkien, Ulmo and Osse are separate from Morgoth, Glaurung and Ancalagon. Meanwhile Enki's status as a god of Wisdom and Prophecy gets taken by Apollo/Asclepius and Hermes/Mercury. Mercury seems to have also been the Planet Enki was associated with in Sumerian astrology. And Apollo has a surprising number of Serpent associations, like Python, the "Spirit of Divination" in Acts 16.
Zeus seems to be both the Anu/El role and Enlil/Baal role depending on the context of the myth, same with Cronos, and Ouranos is the one who's name has the same meaning as Anu, the Heavens. The original from of Zeus/s name was Dios, which like El also becomes a word for god in various forms in various languages, including Theos and Deus. This caries over to the Roman mythology, where Zeus is identified with Jove and Jupiter. I've argued before that the name Jove may be a corruption of Yahuah/Jehovah. Dionysus/Bacchus/Bromis descends from Hadad's vegetation and fertility god aspects.
Gnosticism takes this basic mythological pattern and further complicated it with Platonic Philosophical concepts. Often by identifying Yahuah/Yahweh with the Demiurge/Ialdobath, and the Serpent of Genesis 3 with Jesus.
In Vedic mythology Enlil/Baal is Indra, Enki/Yam is Vaurna, Anu/El is Dyaus, and the Lotan figure is Vritra.
I've talked before about how in Shinto mythology Susanoo can be viewed as Baal. In that context Orochi is Lotan, but I also think Yam can be equated to Ryujin, the Sea-Dragon god ruling from his undersea palace Ryugu-jo. The theory about the Ningi-Jimmu genealogy that suggests it's based on Jacob and Joseph, puts Ryujin in the position of the Egyptian Priest of On, father of Asenath. Which could be interesting in light of Egypt's relevance so far.
Other Far Eastern mythologies have Dragon King gods as well. From the Arabian Knights, the tale of "Abdullah the Fisherman and Abdullah the Merman" also involves an undersea civilization. Job 26:5 says "Raphaim are formed under the waters, and the inhabitants thereof". Which can be interesting to compare to Psalm 74:13.
Rob Skiba talks about understanding The Bible from a mythological POV. Much of where he goes with that I disagree with, but perhaps we should consider that the Beast "rising out of the sea" might be more literal then we at first assume?
The Greek word translated Sea in Revelation 13:1 is Thalassa, which in mythology is the name of the wife of Pontus, the most primordial sea god. Thalassa was identified with Tiamat by Berossus, in which context Pontus is equated to Abzu of the Enuma Elis, in which Tiamat is slain by Marduk son of Enki. But originally Abzu was just the name for the Abyss, the Enki Temple in Eridu was called the E-Abzu. Thorkild Jacobsen has hypothesized that Abzu was an early form of Enki.
Pontus happens to also be very phonetically similar to the name of a Kingdom in northern Turkey who's royal family in the Hellenistic and Greco-Roman period was mingled with the Seleucid Dynasty.
Most assume the "Seat of Satan" in Pergamon/Pergamos was the Altar of Zeus, but I've argued on this Blog it was the Temple to Serapis. Serapis was a Hellenistic cult that combined the Egyptian gods Osiris and Apis. But Samuel Noah Kramer argued that Serapis was Enki.
While this kind of comparative mythology research is fun, it's important never to forget that The Bible is strictly monotheistic. God The Father and God The Son are the same Person along with The Holy Spirit. But Satan is merely a created being, the most powerful created being perhaps, but still merely created.