My commentary on the video ...
Totally agree with your analysis. I would only add that it would have been a good idea to man the walls with archers who were armed with quivers of Obsidian tipped arrows, and behind them spear men with Obsidian tipped spears. Between those, light armored skirmishers with ... you guessed it ... Obsidian daggers. As it only takes one hit with this kind of magical weapon to destroy a white walker, the Night King would have had a much harder time dealing with the defenders in this case. I also would have put the light Calvary behind the castle and used them for flanking action with their flaming scythes. The heavy Calvary would have been used as a supporting force, and given as many flaming and Obsidian weapons as possible. The purpose of this would have been to keep the white walkers focused on the castle wall, their only option for attack. To make it even more likely, I would have had a narrow wooden bridge over the trench made of wood that faced the wall (not the main gate) on the right side of the castle. This would have caused the white walkers to pour over the trench at a specific location (they are stupid, remember) and face the base of the wall. One dragon could have sat on a tower above the wall, and roasted the white walkers. If too many began to pile up, you can then buy time by burning the wooden bridge and forcing the remaining white walkers to have to cross the mote, which if sufficiently deep could have taken quite some time... and once it gets pretty full, THEN ignite the entire thing which you would have cleverly filled the bottom of which with wooden stakes and ... lots of flammable materials and oil. One torch and Kafoooooom! It would then take even more time for the fires to die down so the white walkers to refill the trench... and of course you have plenty of oil ready to refill on top of the white walkers by flying the dragon over the trench and pouring the oil into it... once again, let it fill up with white walkers and once again Kafooooom!! ... all of which would have really pissed off the Night King as at this point he hasn't even gotten his zombie army to the base of the wall for more than a few minutes before they get roasted to ash by the dragon. I would also have recommended, as suggested, to BURN all of the corpses in the crypt BEFORE the Night King got there. Ahem. Meanwhile... wait for the Night King to show up on his undead dragon, and then the two dragons can take him on, as what happened during the show. And yes, I agree... putting Bran in the garden was a risk primarily because the garden is only defended by a relatively low wall, and so there's a good chance the zombie army would simply ignore the castle and move to overwhelm the garden wall. So putting Bran there was dumb... except that he probably was interested in staying in close proximity to the heart tree even though it didn't actually seem to afford him any special powers in the show. But lets assume that Bran would be played VERY differently if we played this out. For one thing, I would have been using him to ATTACK the Night King using every means at his disposal, and interrupting every magical attack the Night King waged as he could... drawing as much power from the Godswood as possible to do so. In which case, if being in the Goodwood was required for Bran to wage his attack then ok fine ... but mount a large Obsidian laden defense of archers and spear men and skirmishers on the garden walls as well, and dig a heavy moat around it. As for how to dig such a moat... it's a magical world and Bran is the premier magician ... surely some elemental force could have helped with that. The roots of the wier trees digging motes seems perfectly viable to my mind. Not only that, but once dug, I would also venture to suggest that those weir tree roots might be just the sort of magic that could entangle undead and crush them as they try to cross the bottom of the moat as well. Additionally, Bran could have had an escape route planned so that once the Night King came within the Godswood to attack, the wier trees could help defend him, and the Obsidian and flaming sword forces could attack the Night King on mass, and Bran could retreat into the caves and hide there.. or make his way into the castle.
The plan that we saw executed on the show seems dumb in every way to me. Perhaps if Tywin had been there... ? Oh well.
With a defense as outlined above and in the video I think the Night King would have had a really hard time. In fact, if I were him I'd have thought long and hard about this attack in this case. Of course there is one thing he has to his advantage. He can raise undead... apparently as many as he wishes, and without limit. Anyone who is dead can become a white walker at his command, whether he killed them or not. So ... the Night King could have simply besieged the castle at this point, surrounded by a wide and diffuse undead army, including undead wolves, bears, birds, etc, dotting the country side for miles and miles around, not letting anyone in or out ... this would have been a cold war brought on because the defenders were smart not stupid thus forcing the Night King to be smart as well ... and bring on the Long Winter with freezing winds and icy storms ... and slowly but surely starve them all to death over a few months - or even years - what does the Night King care how long it might take... he has the entire Long Winter to wait. And as the defenders individually die off, immediately raise them into zombies to run around and kill whomever they can next to them... or hunt for Bran and try to kill him. With the Long Winter bearing down upon the them and the relentless Night King, Lord of Winter, silently waiting for them all to die so that he could get his hands on Bran, and fulfill his wish... what could they have done? At that point I say, well... sorry but... Night King isn't stupid, and he plays the long game ... A Long Winter War of slowly grinding attrition against the living would have been, as far as I can tell, an unstoppable doom upon Winterfell and eventually the world. And so Valaryia was destroyed by fire, and then the rest of the world was destroyed by ice. A well rounded story. The Song of Ice and Fire.
As a Gamemaster, if it were my world, and I were playing the Night King as an NPC, and my players were playing the defenders AND playing them SMART... that's how this thing would probably have gone down. Just saying.
