Me after reading all 12 "History of Middle-earth" books, the two-part "History of the Hobbit" books, and "The Nature of Middle-earth": I pass the test. I will diminish, and go into the West and remain Mitchell.
UPDATE (10/25/23): I gathered a LOT of the important bits of information in here so I don't have to suffer through this one again, lol. Here it is for your reading pleasure:
Thingol did not want to go to Valinor, but he ultimately decided to go due to his love for Finwë.
Ingwë, Finwë, and Elwë/Thingol were direct descendants (in the sixth generation) of Imin, Tata, and Enel (the first Elves to awaken).
The Valar sent Five Guardians to watch over the Elves at Cuiviénen, and they were led by Melian. The Five would go on to become the Istari in The Lord of the Rings.
Elves had a lot more children in their beginning in comparison to later Ages. They have fewer children in each Age until (eventually) they stop having them altogether.
The Ainur's "human" appearance is a mere aesthetic choice. They can cast it off whenever they wish to. However, when the Ainur begin doing "human" things, they become more and more bound to their forms. Melian becomes bound to her form when she bears Lúthien.
Mortal aging slowed in Lórien.
The Elven rate of aging meant that Arwen was the equivalent of a 32-year-old woman when she met Aragorn. Arwen joined the normal mortal aging rating when she had Eldarion (i.e. she began to age at Aragorn's rate, which was slow for other mortals but very quick for her). She died when she was the equivalent of an 84-year-old woman.
Eldarion lived for 120 years. He retained his youth for 60 years and aged for the remaining 65. His children lived to be 80-90 years.
Eärendil's choice extended only to Elrond, his children, and Elros. It would not have gone past the second generation (i.e. if Arwen had chosen immortality and had had a child, then that child would be of the Eldar and would not have a choice in the matter).
Tolkien changed his mind a lot on this, but I think this was his final conception: Elves were in the womb for 3 years, developed full speech at 6, full growth at 72, youth lasted for 6,912 years, and they began to fade after 13,896 years.
Celebrimbor coined the name "mithril." It was called something different before, perhaps?
Pengolodh (the prime source for the information given about the War of the Jewels in The Silmarillion) was the greatest of the Lambeñgolmor (Elven Loremasters) and knew Vanyarin/Noldorin Quenya, Telerin, Sindarin, and archaic Khuzdûl.
Pengolodh finally fled Middle-earth at the end of the Second Age when Sauron arose in might.
Celebrían was born in Lindon at around SA 300.
Númenóreans reached maturity at 24, began to decline at 210 years, and they typically died at around 230 years.
Thingol and Olwë had pale (almost white) hair.
Gil-galad had silver hair.
Eldarin men were around 6'5" or taller and Eldarin women were 6 feet or taller.
Gandalf knew more about wildlife than Radagast.
Númenórean (male) average height was 7 feet.
Indemmar: the ability to project visions into another's thought.
Osanwé: telepathy. It could technically be done by anyone, but it was much harder for the Eruhíni due to the fact that they had physical bodies. The Ainur were the best at it (because they did not have hröar). Elves were much better at it than Men. This is (presumably) what Gandalf, Elrond, and Galadriel were doing in the chapter "Many Partings" in LotR. It can also transcend physical distance (meaning you can communicate with another thousands of miles away).
Osanwé only works if both people are "open" to it. If one closes their mind to the other, then it cannot be done. Morgoth had to trick people into leaving their minds open to him.
Morgoth was a master linguist and could speak any language perfectly.
Órë: true feelings on what is happening or will happen in the world (similar to people saying "my heart tells me this is right/wrong, etc.).
Men were originally supposed to be like the Númenóreans (mortal but long-lived), but their lifespan was diminished after falling to Melkor in their beginning. Númenóreans were just a restoration of that original mortality rate.
Erma: the original, undifferentiated substance that all subsequent things come from. Patterns form from erma that create individualized materials out of it, and these individual materials are called nassë.
Durin is not reborn. His fëa (in Mandos) just returns to his preserved body occasionally.
The fëar in Mandos can look through the eyes of their living loved ones to see what is going on in the world.
When Eru directly intervenes in Eä (beyond what's stated in the Ainulindalë), it's called "The Finger of Eru."
Oromë taught the Three Elderwomen of the First Elves (Iminyë, Tatië, Enelyë) how to make lembas. This became known to the hávanissi (bread-women) of the Eldar. Only Elven-women knew the custom and only Elven queens could keep and distribute it. The special corn was brought and preserved by the Noldor when they came back to Middle-earth. Manwë and Varda ensured that the lembas remained pure and incorrupt throughout the First Age. After Morgoth was defeated, Galadriel was considered one of the chief inheritors of the art in the Second and Third Ages. She taught it to Celebrían and Arwen, and once Arwen died, the art of lembas-making was lost forever. Galadriel personally made the Fellowship's lembas.
Dwarves did not like agriculture and only relied on it when trade was not an option.
Doriath was almost entirely a woodland realm (except on their eastern border, where they had some open land to raise cattle. To the east of Doriath, the Sindar utilized the open prairies to grow food, and both Thingol and the Dwarves relied on them for trade.
The best iron in Middle-earth was found in Thangorodrim.
The settlement of the Vanyar after they left Tirion was called Ingwemar.
Gondolin was the only "fully-realized" Noldorin city in Beleriand.
The Sons of Fëanor came up with the name "Felagund", which was adopted by the Dwarves. Sindarin "phelga" refers to small animals burrowing into holes, so the name was originally given in derision.
The caves were already established by the Petty-dwarves before Finrod came, but he enlisted their help in creating Nargothrond. After paying them handsomely, Mîm (their leader) tried to kill Felagund in his sleep. As a result, they were all exiled.
The exiled Noldor primarily lived in Tol Eressëa (a specific part of the island) after leaving Middle-earth and could only go to Valinor and Eldamar for short amounts of time. They were still under the "ban", even after they were pardoned.
In some of his final writings, Tolkien definitively states that the Eagles are Maiar.
Rabbits were not native to Middle-earth and were introduced by the incoming Númenóreans.
Bears were tame and friendly with the Númenóreans. They'd sometimes go to Men's houses and be given honey.
The "Great Bear Dances" were strange dances performed by the bears, who were instructed by Men. Sometimes the bears would perform their dances for the entertainment of their human friends. The most famous of these was the Great Bear-dance (ruxöale) of Tompollë in the Forostar. In the autumn of every year, Númenóreans from around the island would travel to attend. Even though it looked comical, it was important to never laugh, which only confused and angered the bears.
There was an eyrie of golden eagles on top of the king's tower in Armenelos for 2,000 years. The king personally fed them. They departed when the Shadow came to Númenor.
All the eagles in Númenor were sacred to Manwë. The eagles never attacked the Dúnedain until the Shadow came.
It took many expeditions to settle all of the Edain on Númenor. It did not happen all at once. Elros led the first fleet to Númenor with a big fleet (anywhere between 150 and 300 ships), but many came after over the next 50 years. All the ships were steered by an Elven captain under Círdan's rule. The Númenóreans learned the art of shipbuilding from these Elves, and they created their first boats once on the island.
Númenor was 180,000 square miles.
200-350,000 Edain emigrated to Númenor at around SA 50. 2 million people lived in Númenor at SA 1,000, and there were 15 million at the time of the Downfall.
Archery was a sport enjoyed by both men and women in Númenor. It was just a sport in the beginning, but it became their most deadly skill during their later imperialist conquests of Middle-earth.
All Elves in Arda (both in Aman and Middle-earth) will fade. It happens much quicker in Middle-earth, though.
Galadriel and Celeborn regarded as "High Lord and Lady of the Eldar in the West" by the mid-Second Age.
Sauron thinks Galadriel is his equal.
When Imladris was initially founded, it was largely populated by refugees from Eregion.
All ancient technology used by the Eldar that was of uncertain origin was credited to Fëanor as a default.
Ñaltalma was an ancient Eldarin device that could signal to other Elves from afar (similar to a heliograph). It was small and the flashes were so quick that it could not be observed by Men. Because its origin was uncertain, it was attributed to Fëanor. However, this was likely untrue.
Telerin is the most unchanged Eldarin language.
There were many great Orcs in the east that were not a part of the War of the Jewels. They were not initially subservient to Sauron during the Second Age, and they laughed at his Annatar form. It took around 90 years after he forged the One Ring to get these Orcs under his control and build up his armies.
Dwarves had a latent linguistic passion that activated once they came into contact with other cultures.
The idea to cut runes into stone was first thought of by the Dwarves (specifically those who knew the Sons of Fëanor).
Minas Anor was initially less important than Minas Ithil, which had the most task of watching over the deserted land of Mordor. Minas Anor was chiefly used to guard the Tombs of the Kings, and it was built around the hill Amon Anor.
The Nazgûl can always perceive that the Ring is near, but it can be distorted. It was distorted when Khamûl was near Gildor's Elven company, and it also becomes distorted near water (especially bodies of water with an Elvish connection).
Dol Amroth is the capital city of Dor-en-Ernil (Land of the Prince).
All Elves were skilled at shipbuilding, but it required more skill to build ships that could endure the dangers of the Sea for long periods of time.
Gondor was initially occupied by the Faithful Númenóreans who intentionally named things in Sindarin, which was a forbidden tongue in the later days of Númenor. They made some errors in translating the original nomenclature over into Sindarin, or combining Quenya and Sindarin forms into one.
The full beacon system was established when Rohan came into being, and it was chiefly used to warn both north Gondor and Rohan of danger. There were smaller beacons and greater beacons. When things were especially dire, all the beacons would be lit up (including the lesser ones), but oftentimes the smaller ones were not lit. All the beacons are being lit when Gandalf and Pippin see them.
The Dead Men of Dunharrow were "Men of Darkness", and the Paths of the Dead was likely a place of ritual and worship. When Baldor (son of Brego) went through, the Dead Men broke his legs and left him to die.