And as a little personal contribution, my smol guide on how to get through Deep Caverns as quickly and painlessly as possible. This would be well known by experienced players, but may be useful to newcomers or people who drop their runs on reaching DC. This presumes not collecting mutagens though.
Crucial gear
CAU armor + biohazard boots + aegis helmet
This gives you 100% acid and bio resistance, making certain enemies completely harmless. Just make sure to keep an eye on its condition lest you lose protection in the most unfortunate moment.
CAU armor could be obtained during respective protectorate/free drones questlines. In case of protectorate, check on Frazer after gassing the drones, he will give you the suit as a gift from Mareth. If siding with drones, it could be obtained during planting explosives mission. Trio of CAU soldiers will appear after alarm gets triggered. They are boss characters and have x4 HP, so to make matters easier you can kill the entire base stealthily and trigger the alarm yourself. Alone, they're not much of a threat.
Biohazard boots could be found on a map just north of crimson meadow entrance in expedition, in hive infested area. No need to kill the hives if you don't want to, just stealth past one hive and pick them from a locked box. Requires high hacking, if you don't have it, Constantine rarely sells a pair. Hard to get them without trader refresh this way though.
Aegis helmet is the easiest to get, just join the aegis and get one. Could be replaced by regular gasmask, but aegis helmet is better as it has more durability.
Tesla armor + electropadded boots.
This gives you 100% electric resistance and makes coil spiders harmless. Just make sure to unload all charged gear before engaging them, no harm, but it's annoying to reload it after getting emp.
Tesla armor sits at lemco in expedition, in spider infested warehouse.
Boots require at least 130q of galvanic padding to reach 15% res. Don't know where to get it reliably, I'm usually lucky with drops and merchant inventories. Leather doesn't matter.
Fursuit/ninja suit + good tabis.
Not strictly necessary, but makes you move faster and minimizes the time spent at Hollow Earth. Fursuit also makes rathounds friendly, and DC has quite a number of rathounds.
Lemurian engineer suit + electroinvestigative belt
Engineer suit sits at nexus of technology, belt is given at the institute if you join electric department. Engineer suit provides good bonuses all around, but in context of DC you may bring this gear to reach 140 electronics, would be needed at Arke. If you already have 140, or can't reach it, not really necessary.
JKK jacket/heartbreaker armor + heartbreaker tapki + white dude cocktail.
Once again not necessary, but bonuses to persuasion improve echoing soliloquy feat. Don't bother if you already have 150 effective persuasion.
The route
After getting to DC and talking with Six, immediately go to mushroom forest. The game wants you to use biohazard suit, don't do this, it's awful. With aforementioned set-up, the chompers would be the only psymorphs capable of damaging you as they deal mechanical damage, kill them first. Styg was merciful and we no longer have to stack spore infestation, the area to the far south has a hole we can jump right down to reach the heart.
Afterwards we are forced to go through the hollow earth. Take on your fast gear (fursuit, tabis), if you have Sprint, spam it and spam combat mode. Dread doesn't stack in combat mode, so, depending on your MPs, you can cross the half of the map without getting a single stack. Don't enter stealth before you get the eye debuff. Hollow Earth is completely devoid of enemies (sans one campy industrial bot), and stealth only slows you down. Enter stealth, obviously, only after getting the eye.
The first area has nothing of interest, there's a bunker right ahead to drop dread stacks. Head down east then.
The next area has Leo's knife on one of the tchortists, pick it up and leave south towards Caerus.
Here's when sucking to Faceless starts paying off. They won't help you much, but at least won't be hostile. Faceless patrols are nothing special, but respawning gaunts could be a major asspain. You can kill Faceless mindreader to save Buzzer and still have them friendly by the way.
Corner around hollow earth and move north until you reach the three-way intersection. To the west is Leo - give him the knife, get the feat, pick one hydraulic fluid canister and leave. Leo sells stuff, but he doesn't accept any money, only pure barter.
To the east is the Faceless outpost. Not necessary to visit at all.
And to the north is Arke. As annoying as it is, it had to be done. If you can kill robots quickly, my advice don't even bother with stealth, it will be much quicker and less annoying.
Spider basement could be circumvented with 11 PER check in toxic room, or spiders could be cheesed with Tesla armor.
140 electronics allows us to power all objects of interest, so we won't have to return here later.
Arke bossfight is necessary only to get red AI core for the repair bot. You can skip it and repair the gate manually if you have 115 mechanics and pick mechanic toolset (plenty of those are scattered around), but I say it's easier to go with an AI core - it doesn't weight anything unlike the toolset.
Once Arke is done we backtrack to Caerus. First stop is toxic warehouse we have already passed by, it has hydropneumatic accumulator and two more hydraulic fluid canisters, easiest to get.
Caerus is infested with spiders, so it's Tesla armor time again. Here we need only hs-89 shaft and Maria Hope's keycard in some of the apartments.
The next stop is for you to choose. Hydraulic valve could be obtained either at the end of labyrinth or at Tithonus lab.
Deep worms are harmless with our 100% acid res (just make sure to keep your distance, they can quickly end you in melee), but it's quite a slog regardless.
Tithonus is closer and quicker, but dealing with ghosts is unpleasant if you are not a TC cave wizard. Ghosts have true sight, but their detection range is short, thus, your effective stealth doesn't matter at all. All in all, pick your poison.
After all is ready, we can finally move in. Start from the east, from Faceless territory towards research complex. Step into Tithonus lab to drop dread stacks (and get the valve if you chose this route), exit, go south to make special gas grenades, return to Tithonus. Exit and continue east into the gassed area, drop into a bunker to drop dread stacks again. From here, we have to be really quick.
Once we reach mutagen tanks A gates, we don't really have to go into its basement, we don't need anything here. But this basement allows us to drop dread stacks. It's your call, you may skip it.
Upon reaching Tchort gates, drop the gas grenade and head to the basement. It will, just like the previous one, allow us to drop dread stacks while bot is repairing the gates. Without mechanic toolset, the total weight of spare parts would be just 35 units.
If you move fast and don't stick around you may avoid engaging a single tchortling, as well as backtracking minimized as much as possible.