×bomb on him.

×Should be obvious, but try to buy as few upgrades as possible before the 5th level. And all your upgrades should be +ATK. You need to get your ATK to around 525 to make the fight doable.

×Yellow keys can be sold for 150 greckles each.

×If an enemy is not blocking your way, don't kill it until you have the Lucky Blade.

×Try to kill as many enemies on the 5th level as possible with the Lucky Blade after you've reached the upgrade machine, even if it means taking 100-150 damage from them (though don't be reckless about it). There is a ton of health available on the 5th level, and you need as many greckles as possible to boost your ATK.

×I used the bomb on the adder to get the Really Big Sword early, but it *might* be better to save the bomb for the Slayer. I actually didn't use it much on the 5th level since I was trying to kill as much as possible with the Lucky Blade, but it did let me pick up the Oremite Shield early too.

×Save often.

×Since Gorvin didn't buy any defence at any altar there's something that doesn't add up. Is there another character that grants a defense bonus?

×I realized this after playing "Paycheck".

×In the first version you could get the flippers by opening and locking the first door and walking over all the others Actually, that was the case at pretty much every chain of greckle doors...

×There's a room in 4S5E with a trapped old man, who can grant you 25% boost to HP

×It's possible to defeat the slayer with the lucky blade, with an ATK as high as this. Unfortunately, I wouldn't have had enough HP left over to defeat the archivist.

It's also possible to upgrade your attack to 563 -- you'll notice that I have quite a lot of greckles left, and am about 200 or so short of getting another upgrade after beating the archivist. However, with optimisation and beating the slayer with the lucky blade, you can get that attack upgrade before fighting him.

This run was a fairly good run, but it could definitely be improved. I wasted greckles and yellow keys in certain places where I desperately needed health, and viewed this as more of a 'note-taking run', where I predicted I'd probably fall at the last hurdle and needed to re-do everything. For that reason, I think this run could very easily be optimised a lot further. Are two more attack upgrades possible? 4000 extra greckles is a huge ask, so I'm not sure.

×Avatar source: http://tysontan.deviantart.com/art/Carol-Tea-527178286

×
HP 29715
ATK 521
DEF 362
GR 96
REP 18604
Keys 28/2/1
Expected damage: 20586

×The biggest change in the run was taking an ATK upgrade in the Pirate Lair, allowing me to one-shot Swordsmen without the early RBS. This made enough difference that I was able to kill the Pirate boss as normal. (Before the run, I had considered skipping the boss with the Pickaxe, but it's definitely not worth it -- you get an extra 900GR by saving the Rattlesnake until you can kill it tail-first with the Lucky Blade, and good luck getting the twentieth Machine use without that.)

Credit to Alex Diener for coming up with a much better way to get the Steel Shield:
After reaching the final Machine, I immediately got the Knight Shield and Lucky Blade, then fought my way to the end of Preservation of Tueno as normal, using the Lucky Blade for all fights except Pirates. The Rock Giant gives an extra 500GR with the Lucky Blade, though it isn't strictly necessary to take this, as I finished with 4 spare keys.