This is my latest attempt at reaching whatever's at the bottom. I've learned from my previous mistakes and I believe I've got a better character this time.
I even brought two akhs, a blessed one and a regular one (both lost in this same level). I'm still running out of food and health potions very quickly in the last levels.
The bosses are really taxing in terms of health potions, and exploring takes a lot of time, which means I'm using many food items. Here are my items and skills:
Always keep a torch lit so you don't get sniped from the darkness.
You should be able to dodge all Evil Eye deathgazes and Scorpion attacks with a rogue cloak +10.
Use scrolls of magic mapping and potions of mind vision in demon halls to quickly locate the Demon Spawner so it does not have time to spawn too many Ripper Demons.
Smoke bomb for Rogue tier 4 is a good way to dodge Evil Eye deathgazes if you get caught off guard.
There's 15 upgrade scrolls out there, but I only count +11 on your items.
Assuming none of them were upgraded when you found them, not even counting upgrades from the troll Blacksmith, you're missing quite a few. Or possibly upgraded lower tier items you got rid of, which to be fair can be fine.
It's always a balance, and holding off to upgrade later tier items isn't always best if it means you burn through all your resources at lower levels.
Still, if you'd had a +7 full plate and a +9 weapon, you'd probably be in a better place.
Food:
Figure out fishing.
All levels that have a pool of water and 3 fishes, also have an invisibility potion, which is a valid way to get through to the chest.
If you kill the fish, you can then use their meat as food (never raw, but cooked, charred, frozen or combined with the other items for a meat pie thingy)... but also use the invisibility potion to get our of a jam, which can save you some healing as well.
A spear or whip works from safety/distance, wands of blast work great, fadeleaf and stormvine can work in a pinch.
Mobs :
Abuse the hell out of doorways, corridors, tufts of grass, etc. You should barely ever trade hits with more than one enemy at a time. Surprise attack as much as possible.
Bosses:
lvl 5 boss
Goo should barely scratch your health, find a place near water where you can break line of sight easily enough to get away from its enraged blast. Water to remove the caustic debuff. Don't worry too much about its regen. You should have at least str 12 and a basic str12 season and leather armor.
lvl 10 boss
Tengu has 2 phases, you'll probably take a bit of damage from its ranged attacks, but you should take virtually no damage from its first phase traps.
Drop your flammable scrolls before you reach him, that way you don't burn them if you get caught in fire and they'll be there and intact when you beat him.
Heal with a sungrass if needed between phases. Or wait until you're lower, possibly in the second phase to heal with a potion.
Beginning the second phase, I like to approach at an angle, so I can get out of the way of the large blast while still making progress towards him. A stone of teleport is quite handy here when you get boxed in between 6 lighting thingies and 3 firewalls or whatever.
DoT is nice against all bosses, Tengu included. A simple fire potion can whittle its health a bit without you having to walk as much. A fire seed can work too here, even if he's not walking into it. Just throw the seed on him and throw some non flammable, non-ranged-weapon junk on top, it'll trigger the seed.
lvl 15 boss
big stinky robot. Scout the arena before you trigger its spawn. Throw honeypots you might have at whatever pylons would be more annoying to get to (lots of water or traps).
Once spawned, avoid the red squares of ceiling falling down on you. After each phase it'll be invulnerable, sparks go towards the active pylon. If you're lucky, the active pylon will be one with a bee from the honeypot, and the bee will kill it, allowing you to resume hitting the robot without walking around as much. If you need to get to a pylon, go through the middle area, it'll follow you more slowly while it tunnels through that.
lvl 20 boss
Undead king. Try to break line of sight with the ranged enemies. The throne can work for that as do the statues on the left and right.
lvl 25 boss
Make sure you've killed all the demon spanners in lvl 21-24 (red things that spawn ripper demons). Avoid the laser beams. Fight the hands outside of the central area. Dragon blood elixir is pretty handy here, works great against the fire fist because it gives you immunity to fire, but also against the grass fist because it burns the grass that gives it armor. Craft 1-2 at an alchemy pot
Scale or plate armor plus 10, augmented for defense, and a reliable way to mitigate warlocks and scorpios is a near guaranteed win condition.
Warrior blinding talent is often enough, others I favor are a wand of blast wave to stun or knock them into pits, blinding darts, camouflage glyph on armor, a high level staff of prismatic light for a mage.
If you have the rat skull trinket, for the love of God drop it before going into the demon halls, acidic scorpios are brutal
Pro tip: use all of your upgrades on your armor. A +5 is not enough to tank the enemies and you will burn through health potions. I usually end the game with like 20 of those, just because I don't need to use them.
And I might recommend not to bless ankhs. They give more hp and saturation when unblessed, and you get to save those dew drops for hp, which totals a lot more hp. I think blessing ankhs is just a flex
I prefer to split upgrades - I find there tends to be diminishing returns when I pour too many scrolls into any one item.
+5/6 plate is OK for me for most runs (depends on exact circumstances); after all, armor only protects against physical attacks. Using the rest on weapon/wand/rings can make it so you can avoid taking hits in the first place.
Well, with my strat I barely have to use health potions, and when I do is usually in the early game.
The magic attacks are easy to avoid, just kite the enemies to melee reach. If the enemy is an evil eye I just find a place to be safe while it fires.
I don't need to avoid to take physical hits, because I can just tank. And I love when I have reached a point I can just don't care about the enemies (but magical) and can just walk...
And with thorns, now you can even carry no weapon, they'll just die.
+6 weapon, +6 armor, +6 ring is a nice well-rounded split (yes I know that's +18 and there's 15 scrolls, presumably you can upgrade something that was already +1 or use the Blacksmith).
I usually aim for a more even split, but if anything I tend to sometimes do the opposite of the previous comment and dump most scrolls in a weapon.
Armor only protects against physical damage, and enemies can't attack you when they're dead.
Demon halls get a lot easier when you can one-shot even the evil eyes.
Don't spend your upgrade scrolls on weapons until you get a tier five. You can use one once in a while to you carry a weapon that your strength wouldn't normally allow you to. But if you're bumping it past plus one, you're probably messing up. Save those scrolls for your tier 5 items. I know the one hit is tempting but it's not worth it later in the game.