Right, I've made lots more huge discoveries, so be prepared for a long post! (I'll amend the guide tomorrow at some point, but this is just a forum post exchanging ideas with kmonster and noting down more descriptive bits and pieces of what I've found than will make it into the guide).
So, firstly, the pressing issue of my paladin!
The stats of my paladin are relatively moot as his only requirement was an unlimited supply of Spirit Potions and an unlimited supply of +5 Arrows. The squares are possible this way. However, I see where you're coming from, trying to find a way to slightly improve each stat so that he would need slightly less potions and arrows. This is an admirable goal (though please try to keep any buffs Paladin specific as will be explained later, or, at least buffs that don't require Mages) and his stats were:
Melee: Str24, Dex15, Con10, Int3, Wis21, Cha20, AC30, att 30/25/20/15, dam 13-20, saves 18,18,20, res acid10, cold5, ele5, sp17, gen5/+1, Longsword prof2, Fiendslayer feat
Ranged: Str24, Dex10, Con10, Int3, Wis21, Cha20, att 28/23/18/13, dam 9-14, saves 18,16,20, res acid10, cold5, ele5, sp2, gen0, Bows prof1, Fiendslayer feat
The throwing axes and hammers of all types turned out to be a huge fail. Part glitch and part just mechanics. (More on the glitch later). The mechanics problem with them was that you have to be standing reasonably close to your target to be able to use them and, once you do get one shot off, the enemy is upon you, sometimes getting a sneaky hit if you've cornered yourself waiting for that axe to fly. With arrows and the boots of speed it's extremely simple to run the length of the room and get anything between 2 and four shots off. maybe even 6 if you're lucky, maybe zero if your very unlucky. So, even though the arrows did less damage (theoretically), they made up for it in spades in safety and quantity.
From watching the Youtube video I decided to experiment with buffs. I was interested to know why some of the monsters were attacking him and some not, and why he felt some monsters were better then others.
The end result turned out to be the buff 'Improved Invisibility'.
The mage I imported to test this out was level 11 Mage and level 6 Rouge, so, at level 11, his Improved Invisibility would last the same amount of time as a level 11 Mage who had reached the Squares in normal time.
For this experiment I used my Paladin as he was at this point in the game, not the imported superior one.
I then applied every buff which looked like it might be useful from my Cleric and Mage:
Bull's Strength - Raising his Strength from 20 to 25
Champion's Strength - Raising his Strength from 25 to 27
Spell Resistance - Raising his Spell Resistance to from 2 to 23
Emotion: Hope - Raising his saves to 18,17,18, Attack to 25 (Longsword +2) and damage to 12-19 (Longsword +2)
Aid - Raising his saves to 19,18,19, Attack to 26 and Damage to 13-20, +8 hit points to get to 108 hit points
Electric Resistance - Raising electric resistance from 5 to 11
I then applied - Improved Invisibility - ...
And started Rank 1
Level 5, all monsters died, no loss to my hit points
Level 4, all monsters died, no loss to my hit points
Improved Invisibility then wore out
Level 3, I lost 19 hit points to a Yeti
Emotion: Hope then wore out
Level 2, all monsters died, no loss to my hit points
Level 1, all monsters died, no loss to my hit points
Maybe the Yeti just got a lucky critical hit, I thought. I slept and rebooted...
And I applied the same buffs to Rank 2
Level 5, all monsters died, no loss to my hit points
Improved Invisibility then wore out
Level 4, 54 hit points lost to 4 different monsters
Emotion: Hope then wore out
Level 3, 35 hit points lost to various monsters
Level 2, all monster died, no loss to my hit points
Level 1, all monsters died, no loss to my hit points
It was then that I noticed a pattern emerging...
So, for Rank 3, I just buffed with Champion's Strength and Improved Invisibility
Level 4 and Level 5, all monsters dead, no loss to my hit points
Improved Invisibility then wore off, so I slept and reapplied it
Level 2 and 3, all monster dead without loss to my hit points
Improved Invisibility then wore off and I had a go at level 1 'naked'
Level 1, 104 hit points lost to a Cyclops, 53 hit points lost to a Zombie Lord and death by Umber Hulk.
I had to re-do levels 1 to 3.
For rank 4 only used the buff Improved Invisibility (reapplying between levels):
At level 5 it wore off during my seventh monster and I died. On my second attempt it wore off on my seventh monster and I survived
At level 4 the exact same thing happened on the sixth monster
At level 3 I timed out against 2 Frost Giants, but won the level
At level 2 and level 1 it was a piece of cake
So, onto rank 5, same method:
Level 5, Improved Invisibility wore off during the 5th or 6th monster (2 attempts) and I could not complete the level
So, back to the drawing board. Time to try and 'speed up' the monster's deaths in order to make Improved invisibility last for more monsters:
I now apply Champion's Strength, Hope, Aid, Haste before applying Improved Invisibility
Level 5, level 4, level 3, level 2, level 1, all monsters die in time before Improved Invisibility wears off
Onto Rank 6 with the new buff selection designed to support Improved Invisibility:
Level 5, Wears out on the 6th monster, but it's an easy one, 7th monster nearly kills me, but I make it
Level 4, Again, wears out on the 6th monster and I have to concede a square, but the next monster is an easy Shadow
Level 3, level 2, level 1, all easy
Rank 7 is when it starts to get really interesting.
Level 5, wears out on the 7th but I make it
Level 4, wears out on the 6th, but I make it
Level 3, easy
Level 2, Complete fail - first appearance of an Elder Elemental. First one timed out on me, the second made me run for the concede lever. Next reload the elemental decides to disrupt on the 12th hit and the rest is easy
Level 1, easy
And now the new pattern emerges, everything's fine until the Elder Elementals show up
It then comes down to a matter of attacks per turn. 2 attacks per turn is just not enough to finish off the Elementals in time and one is relying on disruptions from the Club of Disruption
So Rank 8:
Level 5, turns into level 4 after a timed out elemental blocks a square
Level 5, turns into level 3 after a timed out elemental blocks a square
Level 5, fails after an elemental fails to die after 18 hits
Level 5, easy at last, no Elementals
Level 2 and level 1 both easy
So here we wind up at the same point as the guy in the video, hoping for good monster spawns (low hit points) and hoping for lucky and timely disruptions
To conclude: The buffs piled on by the guy in the video are unnecessary.
For the first 4 ranks all that is required is Improved Invisibility (though level 5 of rank 4 may require the following...)
For ranks 5 to 10 all that is required is:
Champion's Strength (level 5 Cleric) or Bull's Strength (level 2 Cleric)
Aid (level 2 Cleric)
Emotion: Hope (level 4 Mage)
Haste (level 3 Mage)
Improved Invisibility (level 4 Mage)
Haste, only lasts 1.5 monsters, but it speeds things up just enough to make a difference in keeping Improved Invisibility going up until the 6th or 7th monster on the higher levels
Emotion: Hope, wore out quicker on my Paladin than it did on the rest of the team, which is an interesting glitch
There are a vast number of buffs which improve this and that, but they only last a few rounds and are generally pointless, particularly ones which relate to AC, resistance and saves and wear out before Improved Invisibility
Stoneskin is useful for a bit of security when facing the last monster on level 4 and 5, but, again, not at all necessary
Now for some glitches:
Improved Invisibility is the key to the Battle Squares because not one of the monsters recognises it. They just stand there as if you were invisible. It's like chopping down trees. Unless this glitch is unique to my version
Some of the Demons would take 12 or 13 hits with the Club of Disruption +3 at 14 points a hit, but would die after just 5 hits from my Longsword +2 at 20 points per hit
I got none of the teleporting glitches shown in the video, it must have been one of the buffs he used which causes it
The Club of Disruption uses Crushing damage and usually dealt 14 hit points of damage (bony undead aside), yet my +2 Hammer with additional electrical bursts only dealt low single figure damage against the same foes (bony undead aside). This was also the case for throwing hammers and axes (hence why arrows were better, averaging 10 points of damage)
The Remorhaz gets stuck in the doorway, just exit the north door and missile attack if they prove problematic
Emotion: Hope is cast on the entire party, and yet it would wear off of my character during a fight but when I was returned to my team, they all still had it in effect
Against some of the monsters my character would stop fighting when Haste wore off. I had to walk him away and reassign him to attack to reactivate him
And finally:
My mage could cast level 4 spells at this point in the game but did not have Improved Invisibility in his list of spells, if I remember correctly the first person selling this spell is the mage lady in the Fell Wood camp? Or can it be 'found' or bought earlier?