Q: So the Valar killed Morgoth and then they (and the Calaquendi elves led by Finarfin) just went back to Valinor?
A: No, not exactly. Morgoth is unkillable. The Valar cast him into the outer darkness (where Ungoliant came from). Also, they sunk Beleriand, as revealed in the link at the end of the previous section.
Q: What happened to Maglor and Maedhros?
A: After Morgoth was torn screaming from his citadel Angband and his crown cut from his brow, the two remaining silmarils were in the hands of Eonwë, a Maia servant of the Vala Manwë. The two surviving sons of Fëanor approached him and very politely demanded the immediate surrender of the silmarils, in accordance with their Oath.
After Eonwë finished laughing and realized they were serious, he told them what they could do with their Oath, and they slunk away with their tails between their legs. Alas, the Oath couldn’t be scolded out of someone; they returned that night and stole the silmarils away from Eonwë’s camp.
At this point they discovered that the holy light of the silmarils burned them, exactly they way it had burned Morgoth when he stole the silmarils. The silmarils were holy things, and Maedhros and Maglor were steeped in the blood of their kin.
Each of the brothers took one silmaril, while wearing gloves. Overcome with remorse, Maglor carried his immediately to the nearest Crack of Doom and leaped in with it. Maedhros found a high cliff and threw his into the sea. Then he wandered the shores of Middle Earth for ever after, telling his sad story and warning others of the price of hubris. As far as I know he was still doing this by the time of Lord of the Rings.
Q: Well, that’s two silmarils gone. What about the third one, the one that Elwing carried?
A: The third silmaril was instrumental in permitting Earendil and Elwing to access Valinor, as told in the story we mostly skipped. After Earendil successfully petitioned the Valar to intervene and save Middle Earth, he was rewarded by being turned into a constellation, with the silmaril a star on his breast. Elwing, who had learned how to turn into a seabird and also how to talk to seabirds, lived in a high tower in Valinor and whenever Earendil’s star-ship reached land, she would fly out and visit him.
This makes perfect sense and we are done discussing it.
Q: What about all the elves and humans who lived in Beleriand? Did they all drown?
A: Only the bad ones. The good humans, the Edain, were given a special new island the Valar built specially for them: Numenor. The good elves were given a full pardon for all their various crimes and a free ride on a magic island home to Valinor.
Q: Did all the elves go to Valinor, then?
A: Nope! Some, like Galadriel, were still proud and haughty and unwilling to admit that the Valar had been necessary to save them and so on. Others had never been to Valinor and didn’t see the appeal; it’s not as if they still had the light of the Trees there, after all. So Gil-galad, Galadriel, Elrond, Cirdan, and Celebrimbor all chose to remain in Middle Earth. They went east and encountered the Nandor, the elves who were already living in the regions we think of as Middle Earth. The Nandor were mostly descendants of the Avari and had stayed out of the whole history of the First Age by keeping their heads down. The Noldor and Sindar (by this point essentially one people) colonized them.
Legolas is elf royalty in Mirkwood because he’s descended from the Sindar elves of Doriath (specifically he’s the grandson of Oropher, who I think was in charge of keeping Thingol’s kitchen tidy or something minor like that).
Gil-galad refounded Lindon, in the northwest, and Celebrimbor and others went east to Rivendell. Galadriel went further east, to Lorien.
Q: Does that bring us up to the present?
A: Not quite! There’s still the matter of the Rings of Power and the Last Alliance. And a lot of boring stuff that there’s no reason not to skip over; Tolkien didn’t even bother to write most of it out.
Q: Okay then! Rings of Power: lay it on me.
A: That’s not a question, but okay. Celebrimbor was in Rivendell, making stuff the way his grandfather Fëanor used to make stuff, when he was visited by a stranger. Annatar the Gift-Giver was his name, and he was Maiar or something. He’d been around in Middle Earth for a while, he said, and he knew a bunch of secrets of crafting.
“They call me Annatar the Lord of Gifts because I like to give people things! I especially like to give them magic rings. I have no ulterior motives whatsoever!”
Celebrimbor was at the time mired in a major project, crafting the Rings of Power. He’d just finished the first three (one for Cirdan, one for Gil-galad, and one for Galadriel), but Annatar helped him make seven to give to the dwarves and nine to give to humans.
But then! Annatar was actually Sauron, Morgoth’s apprentice! Oh no! Sauron created the One Ring to rule the seven and the nine, and revealed himself as being a big jerk rather than a guy really eager to give rings away.
(Later, in the Third Age, when Gandalf, Radagast, Saruman, Pallando, and Alatar, the Five Wizards, arrived in Middle Earth, they first appeared in the Gray Havens. Cirdan took one look at Gandalf and declared that Gandalf should have Cirdan’s Ring of Power. This pissed Saruman off, as you can imagine.)
Q: And the Last Alliance?
A: So I mentioned Sauron, right? There’s this whole thing with Numenor and Sauron that isn’t worth going into, but suffice to say that Sauron with his rings warred with Gil-galad and the other elf-kings off and on for centuries. Sauron set up shop in Mordor, and bred trolls and orcs and so forth. He didn’t have any balrogs or dragons, because unlike Morgoth he lacked the personal power to command them.
After Sauron indirectly led to the sinking of Numenor (not worth going into, I said) the human descendants of Elros, now calling themselves Dunedin rather than Edain, petitioned Gil-galad to join with them in defeating Sauron. This was the Last Alliance. Big ol’ war. Gil-galad died. Elendil, the king of the Dunedin, died also. But they cut the One Ring from Sauron’s hand and killed him, which ended the Second Age and began the Third.
Q: Anything interesting happen in the Third Age?
A: Elrond, as Gil-galad’s closest living relative besides his great-aunt Galadriel, inherited the Ring of Power from him.
With Gil-galad dead, there didn’t seem to be much reason to have another high king of the Noldor. Cirdan took over rulership of Lindon, but this nation became depopulated as he built ships and put elves on them and built more ships, until it was just the Gray Havens.
Celebrimbor died in the wars with Sauron, so Elrond was left in charge of Rivendell. Galadriel seized power in Lorien and finally became a queen.
As the years went on, more and more elves left Middle Earth. Humans moved into the spaces they vacated, until only pockets of elven presence remained.