Chiligyro

I will say this, the effect of deck thinning just by fetching is so small that it is not worth the life loss. You would be better off just running swamps. Also, with just 18 lands I think you should cut fleshbag marauder or you will have too many 3-drops. You don't have sufficient zombies to make use of gravecrawler.
Overall I think this will make the deck more effecient:
-4 Fleshbag Marauder
-4 Gravecrawler
-4 Polluted Delta
-4 Bloodstained Mire

+9 Swamp
+2 Bad Moon (move from SB to MD)
+1 Mogis's Marauder (move from SB to MD)
+4 Vampire Lacerator

Personally, I would feel more confortable with 19 lands than 18, and you can always discard it to pack rat anyway. You need 4 bad moons in your maindeck, or your beatsticks will be too weak. I have a hard time justifying contested war zone and ghost quarter, in most cases I would rather have a swamp. You also run out of steam really fast, so I was wondering if you have thought about adding bob, or maybe some of those semi-bobs like pain seer and blood scrivener? Because I have a hard time justifying despoiler of souls, at least the other two can block in a pinch, and they provide card advantage.

I would remove the liliana's caress, waste not and underworld dreams and run a full playset of shrieking affliction, stupor and duress. Alternatively, you can run 2 Nyxathid over 2 shrieking affliction. Also, exchange terror for doom blade or victim of night, both of those cards hit more targets than terror. Also, geth's verdict is strictly better than diabolic edict, so you might want to swap them, however, I think gatekeeper of malakir would be better in that spot personally. Also, while I personally love using extirpate in my decks, it doesn't fit the main strategy if this deck, which is keeping the opponent's hand empty. You should rather run an additional funeral charm and some more removal.
The reason liliana's caress is bad in a discard deck is actually straight forward. It does nothing after turn 3, since their hand should be empty by them, making it a dead draw. Also, you don't want to play it early since you would rather play hymn to tourach/stupor/duress/hippie/you-get-the-point. The same applies to waste not. Underworld dreams falls into this trap too, while it looks good on paper, the fact that it does nothing to keep your opponent's hand empty or provide any sort of board control, makes it a bad card.

To finish this wall of text: Have you considered inquisition of kozilek instead of duress? What you want to hit with duress is usually some card that can disrupt your early game plan. Inquisition does this better since it also targets creatures. Realistically a 4cmc+ card in your opponent's hand should have hit the graveyard before turn 4. While you might want duress due to it being the better draw lategame. Consider this, if your opponent keeps a card in their hand to negate rack damage, chances are they could have played it anyway, but chose not to because it would make no difference. This is either a land (roughly 35-40% chance considering most deck's composition), a utility spell or a "bomb"(any card worth with a cmc of 4+). Cheap creatures will generally be played on turn, and utility spells will usually be instants cast in response to either inquisition or duress, so it doesn't really matter which you run. Sure, inquisition does not hit bombs, but neither does duress, since most bombs tends to be creatures.

Sure, I can see see the flavour of Pulling Teeth, however there is also plenty of torture flavour if you read the flavour text of some of the versions of Hymn to Tourach:
"The eerie, wailing Hymn caused insanity even in hardened warriors."
That is psychological torture, or:
"Members of the Order often played the Hymn on instruments made from their victims' bones."
Imagine having our arm cut off and then turned into a flute that plays Hymn to Tourach, yep super creepy.

I just recently came back to the vault (a week ago or so) and I must agree what you have stated about the nature of this site now. Back in the day when I last used it actively (probably 5+ years ago, it was when there were still deck building contests in the forums), the creative juices were flowing a lot better back then than they are now. I did a little experiment myself. I posted my Legacy land destruction deck, fully equiped with duals, sinkholes, fetches and top tier cards in general. It got 0 attention, then I rummaged through my casual budget decks (decks I use when I play with people new to magic, I frequent both tournaments and noobs), which I designed to be powerful synergistic decks for a very affordable price, decks that with a few updates to the mana base and a some other updates and/or changes would leave me no worries to take for a fun spin at a modern FNM. Both of those decks got some attention, so it confirms your theory a bit at least.

So I am back for now, don't know how long, but I think I would rather give critism than put decks up for critique here, since what this site needs is not an abundance of decks, but rather more people knowing their stuff taking their time to help explaining card choices and strategy to people. Which is a reason why it is bad that you leave, but understandable. For the sake of your fellow vaultiers, you should maybe check back once in a while and leave some pointers on some of the decks that catches your interrest in the "New" section. You don't have to post decks in order to use the vault.

Is there any particular reason for you to NOT run a playset of Hymn to Tourach? It it a billion times (maybe more) better than pulling teeth. And it doesn't cost a lot of money either. And I think I would rather have Quest for the Nihil Stone than Painful Quandry. Overall I have this recommendation to improve the deck:
-2 Painful Quandry
-1 Liliana's Specter
-1 Ravenous Rats
-4 Pulling Teeth

+4 Hymn to Tourach
+4 Quest for the Nihil Stone

Another thing is this: I am concerned about the inclusion of Rackling over additional Wheel of Torture, is it purely flavour-wise? The reason I ask is because Rackling probably have the most vulnerable card type in the game, artifact creature.

I would still go for crop rotation over harrow as it lets you search for urza lands too. And maybe remove a couple of chromatic spheres as well so you can play 4 of them. Honestly, I think you underestimate the power of crop rotation.

That could very well have been me, if it was in Lyngby. But I think you are mixing two of my decks together there, they still include a lot of the same cards and given it was a long time ago, I think it plausible to get them mixed up.

Honestly, you need to have more reliable ways to get your tron pieces. Also, mountain valley is dirt, just play extra basic forests. I would recommend following changes:
-4 Ebony Rhino
-4 Mountain Valley

+4 Forest
+4 Crop Rotation

It is interresting, at least for game 1. In game 2 and 3 you should sideboard telepathy out for hard counters though. Since you know what to declare. I am not sure I like prodigy though, I would rather have Daring Apprentice, he doesn't cost mana twice.

You're welcome!

I would remove the life-gain cards, since they do nothing on their own. Instead add Swords to Plowshares and Oust. It also allows you to cut green making the mana-base better, also add Enlightened Tutor.
-4 Healing Salve
-4 Heroes' Reunion
-4 Rest for the Weary

+4 Swords to Plowshares
+4 Oust
+4 Enlightened Tutor

It improves your control capabilities as well as improving your combo.

I think cutting Jace's Phantasm and maybe a single copy of Jace, Memory Adept for more mill. Adding a playset of Alter of the Brood acting as Hedron Crab 5-8 and one more Sands of Delerium (Mainly due to not being fond of 1-ofs).

The reasoning is this: Jace's Phantasm acts towards the wrong goal. You don't want to kill your opponent with damage, but mill. I didn't say anything before due to it being flavourful. And the 3 Jace instead of 4. You want a Jace when you can play him, and not get stuck with 2 early on in your hand. So, hence 3 instead of 4. 1 more sands is to ensure you will actually see it, and having a mana dump is always good.

Funny, I think I actually met you at a modern FNM some months (6+) ago. Personally I played mono-black "mill" there for the fun of it. I haven't had time to play modern tournaments in a while though.

A counter shell is probably the best way to go with blue devotion, since you have to keep you permanents from getting killed or else you cannot trigger devotion on Thassa. The best way to avoid that is to counter the kill spells.

Spells that only mill and nothing else is not usually something you should play unless they mill a lot, since they leave you vulnerable. Instead I would recommend adding Rune Snag and Archive Trap.
-2 Dream Twist (Does not mill enough)
-1 Traumatize (It is bad, only having one means if you get it "lategame" it might only mill ~8-10 cards for 5 mana)
-1 Increasing Confusion (Not really impressive, since it is sorcery speed)
-2 Gitaxian Probe (Sure it gives info, but don't really need it. It is better in combo decks tbh)
-4 Vapor Snag (It is pretty restrictive only targeting creatures)
-2 Mind Sculpt (It is sorcery speed, so you should not cast them before turn 4, since you need couter back-up for enemy turn)

+4 Archive Trap (Has the bonus of being free if they search their deck)
+4 Rune Snag (Better than Mana Leak after the first)
+4 Boomerang (Better than Vapor Snag)
I know it is a lot of changes, and I could go suggest even more changes, but then it would lose some flavour and uniqueness, which you obviously want too.

Honestly, you need some counter spells. Remove Wingrafters, two Hypnotic Sirens, and Teferi (You are not that likely to see him any time you actually need him anyway as a 1-of) and add a playset of Mana Leak and three Spell Snare (or Dissipate). The idea is interresting though.

As a person devoted to playing control and having my main legacy deck atm be land destruction, I know the weaknesses of the strategy. My point about it being too slow is mainly due to the lack of acceleration (besides from Birds) and no Boom//Bust. I personally don't think you need Acidic Slime and Arbor Colossus, and I have played with Avalanche Riders myself before, I am not too fond of them to be honest.

Here is my honest idea of a way to improve your deck, fully explained:
-1 Acidic Slime
-2 Arbor Colossus
-3 Avalance Riders
-1 Mwonvuli Acid-Moss
-3 Mountain
-3 Forest

+4 Boom//Bust
+3 Trinisphere
+4 Bloodstained Mire
+1 Overgrown Tomb
+1 Blood Crypt

Now, before you call me crazy, and wonder about the Bloodstained Mires, Overgrown Tomb, and Blood Crypt. They are all there because of Boom//Bust. When casting Boom//Bust you can target your own fetchland and sacrifice it in response thus giving you a semi-sinkhole. Also having black mana and a reliabe way to fetch it lets you explore more sideboard options, however I don't know your meta, so I cannot help you there. Trinisphere, yes Trinisphere, it was made for land destruction. However if the fetchlands and extra shock lands are out of budget, just add Trinisphere instead of Arbor Colossus and Acidic Slime.

You miss the point of shriekmaw. They double as a sorcery speed terror. But can still grant board presence if you draw them lategame.

To be fair, with beacon and/or tainted remedy or false cure, it is instant death. So instead of rest for the weary you should add removal instead, like swords to plowshares. I would also remove the dark rituals and the congregate, and max out on false cures and add add 3 wall of omens. You could make it 4 wall of omens if you remove 1 elixir of immortality. Remember, you play a slow combo deck, so protection is vital if you ever want to see 6 mana. And since you only play 20 lands, you need the can-trip wall of omens provide.

You should cut Pain Seers, due to high converted mana cost cards, and Blood Maggots, as they are pretty bad, in this deck. Instead take a full play-set Thoughtseize. I would then use the remaining 5 cards to get another Whip of Erebos and maybe a playset of Shriekmaw.