Like 
Esty I’m not a big fan of the Appendices. There are certainlly some very interesting incidents recounted, but all in all, they are primarily for reference & background. Tolkien himself noted that the only really necessary sections for understandding the story are The Tale of Aragorn & Arwen & the Shire Calendar.
The story of Numenor was a relatively recent invention of Tolkien’s - the original mythology consisted only of the First Age. Yet the image of the great wave overwhelming the land was a recurring one for Tolkien (he gives it to Faramir in the book).
The Downfall of Numenor is yet another story of pride leading to a fall. What begins as a reward for the Edain’s service in the fight against Morgoth ends with the most spectacularly devastating event in Middle-earth history - the very world itself is changed by the direct intervention of Eru. The originally flat world was made round. The strangest thing about this is that there are individuals around at the time of LotR who had lived in (on?) the flat earth.
Its difficult not to feel that the whole Numenor thing was a major mistake on the part of the Valar. The longer life gifted to the Edain of Numenor is what, in the end, produced their rebellion. The fact that they had longer in the world made them desire it more & wish to remain. To situate it within sight of the Undying Lands, allow the Eldar to visit it, & yet forbid the Numenoreans to travel there was bound to lead to  trouble ( the Undying Lands were like the Edenic Apple - pointed out to the inhabitants who are then left alone with their temptation - asking for trouble, one might say.
The Numenorean’s rise seems inexorable, the ultimate challenge to Sauron inevitable. Their fleet & armies terrify Sauron’s armies & humiliate him. There is no mention of Sauron 
himself being daunted by the Numenorean’s. By the time he is captured & taken to Numenor, the Numenoreans are fallen so far that they are an easy prey. Its difficullt to know what he expected to happen to the Numenorean fleet that assaulted Valinor, but what actually happened probably came as a shock.
Of course, as I said, all this is background, & not strictly necessary - the important information has already been conveyed in the story proper (The Shadow of the Past/Council of Elrond chapters) but it does add a sense of depth & of the feeling of a weight of history behind the events of the story.
The story of the Kingdom of Arnor is one of fragmentation & infighting leading to weakness. The Witch king takes advantage of the situation to serve his master to devastating effect, & the result is the fall of the realm. 
I suppose the most interesting event in this section is the encounter of Arvedui with the Lossothclearly a people akin to the Innuit & (more likely, given Tolkien’s love of the Kalevala) the Lapps. 
The Lossoth themselves seem to be of the same kind as the Wild Men of Druadan forest, ‘primitive’ people living in wild places. They are very much in touch, & in harmony, with the natural world. We seem to have a situation very similar to the Homo Sapiens/Neanderthal one in our world.
The oddest thing about this incident is the location. As Alex lewis pointed out in his article ‘The Icing on the Cape’ in Amon Hen 102, the Ice Bay of Forochel is only 250 miles north of Hobbiton. In the Shire the Hobbits grow both grapes & tobacco, both of which require a warm climate, yet less than 300 miles to the north we find arctic conditions - ice only just beginning to break in March (& that ice a long way out to sea). Lewis points out that this means the sea would be frozen solid for over six months of the year.
Tolkien points out that the bitter colds of the realm of Morgoth  ‘linger still in that region, though they lie hardly more than 100 leagues north of the Shire’. As Lewis points out ‘So from this one can see that even Tolkien considered the climactic conditions at Forochel anomalous.’
Lewis comes up with an interesting theory to account for the ice bound state of Forochel:
	Quote:
	
	
		| When Morgoth fought Fingolfin the High King of the Noldor used a sword called Ringil, which was ice-blade or "cold star" in translation. It was described as glittering I Iike ice. This could perhaps have been a magic blade of great power. It would certainly have had enormous powers to be able to inflict terrible wounds upon Morgoth, a Vala. It is worth remembering that Tolkien gave names to things and people with a purpose and those names signified something. Ringil, the cold star has the key to a puzzle for me. ... 
 If Ringil was seized by Morgoth after he defeated Fingolfin and then twisted its powers to his own uses, then an ice-blade, a cold star might have found its resting place in the bosom of the earth under the sea in old drowned Beleriand to the north where Angband lay, which is not far removed from Forochel. ...
 
 So was Ringil overlooked in the general mayhem of the War of Wrath? Had its power been corrupted by Morgoth to remain after him as a constant reminder that his powers were only exiled and not destroyed?
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 Ok, take that with a pinch of salt if you like, but at the very least there’s the potential for an interesting fanfic or RPG there....